In part 1 I discussed the primary monster roles; here, I will move onto secondary roles. The secondary roles are standard, leader, minion, elite, and solo.
These are the bulk of monsters, and they also serve as a reference point for the other monster secondary roles. For example, 4-5 minions equals 1 standard, 1 Elite equals 2 standards, and 1 Solo equals 5 standards. An encounter composed of all standards will typically have the same number of monsters as the PCs, or see the PCs slightly outnumbered. Individually standard monsters aren't much of a threat to an adventuring party, but by working together they can become greater than the sum of their parts.
A leader monster is unique in that it is almost a tertiary role (albeit the only one in the game); leaders can be found among standards and elites, as well as any of the primary roles (though some are more likely to be leaders than others). They don't usually function very much different from a normal monster of their type, except that they have either a trait, power, or possibly both which directly helps their allies. These can consist of offensive or defensive buffs, granted attacks, granted movement, or healing. Not every encounter needs a leader, but it's a good way to mechanically represent the guy that's in charge to make him feel like he's in charge. Prepare to have standards, minions, or more rarely elites directly protect the leader if he gets into trouble, because he will be a priority target. Once he goes down, all of the other monsters get worse at what they do (depending on how significant his abilities were).
I'm of the opinion that minions were one of the best things to come out of 4e. Each minion has only 1 HP and their attacks are extremely simple (they have set damage instead of rolling for damage), so they require virtually no book-keeping on the part of the DM aside from removing their minis/tokens when they die and remembering their initiative order. They also allow you to run balanced encounters where the monsters vastly outnumber the PCs, which tend to be cinematic affairs with PCs mowing through their foes. Just because they're pushovers though, doesn't mean that they're not deadly. They're designed to swarm around PCs, threatening them with many OAs, blocking off squares, and causing high damage attacks to be wasted. Even if each of them attacks for relatively low damage, that damage can really start to add up! Besides, they have the normal defenses and attack rolls for their level so despite being easy to bring down, they're not necessarily any easier to hit. Best of all, they add tactical variety to the age old single target vs multi-target damage issue. Before their introduction into the game, single target attacks were obviously superior because injury doesn't impair a monster's ability to fight until it's knocked down to 0 HP. Therefore, it's in everyone's best interest to take single-target attacks (which deal higher damage per target) and to focus fire on a single enemy, bringing it down as fast as possible so that next round it isn't present to attack. Well, that's a bad idea when dealing with minions. AoE attacks are the way to go here, because you can wipe a whole swath of minions off the map with a single action. Focus firing on stronger enemies is still a very useful strategy, but now the game rewards the multi-target strategy as well (that's not to say that multi-target PCs are simple glorified minion poppers; multi-target attacks also allow you to spread status effects to more enemies, and to finish off severely injured enemies while simultaneously softening others up).
I would highly recommend that encounters featuring minions also featured them in waves. This way if the controller gets rid of all of the minions in round 1 there will be more to harass the PCs later. It's also important to balance having minions swarm PCs to overwhelm them (where they're vulnerable to AoEs), or to keep them safely spread out (where they're less likely to be as annoying). One of my favorite tactics is to use artillery minions that can focus fire on PCs while staying spread out at the same time. This shouldn't be the only way to use minions, but it's a good way to keep them around longer. Just remember that most PCs like clearing a half dozen enemies at once, even if you might be slightly disappointed that you didn't get to "use" them. Even minions that die right away have done their job, by putting a grin on the face of the player that single-handedly took them all out.
Minions tend to interact differently with PCs of different roles, so keep in mind your party makeup when designing encounters. Strikers hate minions, because any time they attack them is a waste of their high damage (the exception being the Sorcerer and Monk, who have plenty of AoE attacks in their repertoire). Defenders usually aren't fond of minions either, because the number of marks and/or punishments they can dole out are limited, and so they typically want to go after the toughest-looking soldier or brute and keep him busy while the other PCs finish everyone else off. Defenders also typically work with melee strikers to protect them as they slaughter priority targets, and minions can a) keep the defender from getting to those targets and/or the striker, or b) harass the striker despite the defender's presence, since he can't stop all of them. That said, a defender provides very effective area denial against minions, who can't afford to take a single OA because of their single HP. Controllers love minions, which shouldn't come as a surprise. They have the greatest selection of AoEs and multi-target attacks, in addition to zones and walls which are a hindrance to most monsters, but downright lethal to minions. The very threat of a controller's AoE may be enough to prevent minions from clumping together to focus fire. A Leader's opinion of minions often depends on their secondary role or the party make-up, since a leader's main job is to act as a force multiplier and make everyone else more efficient. If a leader can buff a controller's attack he may like minions just as much as that controller. An enabling leader, on the other hand, just wants to give the striker extra attacks, and he doesn't want to waste those on minions any more than the striker does.
Elites are relatively straightforward, in that they are beefed up monsters meant to count for 2 standard monsters. This alone makes them priority targets, since killing one eliminates 2 monsters from the field. Their high HP makes them able to endure roughly twice as many attacks, however, so it's much tougher for PCs to bring them down early. Because of this they can be "trap" priority targets, since it's often more efficient to take down weaker enemies first to reduce the amount of incoming attacks. Beware of controller PCs, however; each successful status effect applied to an elite reduces your side's effectiveness twice as much as it would a standard. Furthermore, elites are less likely to have effect-shaking abilities like solos (though they do get a saving throw bonus). The most important piece of advice on Elites, however, is to look it over before you use it!!! Many elites from earlier sources may have had double the HP of a standard, but only slightly higher offensive capabilities. An elite's attack should deal roughly twice as much damage as a standard monster of the same level and role, whether that comes from stronger attacks, the ability to attack multiple times per turn, or significantly more powerful recharge or encounter powers. Also keep in mind that elites get an action point, so they're able to front-load their offense very efficiently (use it early to really frighten the pants off the PCs!!!). Elites tend to be slightly more complicated to run, as they often have more "big hit" powers (recharge or encounter) and more traits. As a final note, don't be afraid to provoke OAs with your Elites; they can afford to take the hits, and if it gets them into a favorable position it may be a good move (also, movement makes a combat dynamic).
I'll lead off with a warning here - examine any solo monster carefully, and as a rule outright avoid the ones published before MM3 unless you personally tweak them. Because a solo counts as 5 standard monsters but is wrapped up in 1 body it has a significant impact on how an encounter plays out. First of all, AoE powers are reduced in effectiveness, as are powers and class features that trigger off of bloodying or killing enemies. Status effects, however, have the potential to completely shut down the encounter if the solo is improperly designed. Save penalties can often cancel out the solo's save bonus at high levels, allowing a controller PCs to remove five monsters from the fight with a single status effect. Newer solos get the ability to shake off the more powerful status effects more easily, somewhat ameliorating this weakness. Another potential pitfall is that a solo battle could turn into one where the PCs all crowd around the monsters and both sides exchange blows. Well-designed solos will be more resistant to this outcome, such as the new dragons that get a move + attack outside of their normal turn. And that brings us back to offense. A solo needs to have even more reliable offensive output than an elite. This is usually accomplished through one or more of the following: making multiple attacks per turn, making attacks in response to triggers (like being hit), having impressive "big guns" powers, and getting multiple turns in the initiative order. Solos also have 2 action points. A solo's stat block is usually much longer than that of a standard monster's, with a lot of different triggers, recharges, etc. to keep track of. Still, you're only running the one monster in place of 5, so it evens out.
Finally, my biggest piece of advice is not to take the term "solo" literally! A well-designed solo encounter will feature an at-level or level +1 solo, with a smattering of other monsters to ramp up the total encounter difficulty to level +3, 4, or even 5. A solo is most often the BBEG (Big, Bad, Evil Guy) that the party has been searching for, defeating many encounters with his lackeys before confronting him. BBEG's don't get where they are without being intelligent, and an intelligent creature will have his minions do some of his fighting for him! A solo can usually put off getting attacked for a few rounds while the PCs deal with his underlings (which they should do; it won't take very long to kill them, and killing them reduces the amount of attacks that the PCs need to endure. Imagine going for the solo for 5 rounds while suffering from not only his attacks, but also his minions for that whole time!). Have solos fight smart, and keep in mind that they got to be so powerful by surviving. They'll very rarely fight to the death unless absolutely forced to, which gives you a perfectly believable excuse for "calling the fight" early, especially if it ceases to be exciting. Solos have a LOT of HP, but if they know that they're not going to defeat the PCs they certainly aren't going to stand there while they whittle away at it. As with Elites, don't be afraid to provoke OAs with solos, especially early on.