Each character class specializes in one of four basic functions in combat: control and area offense, defense, healing and support, and focused offense. The roles embodied by these functions are controller, defender, leader, and striker. The classic adventuring party includes one character of each role: wizard, fighter, cleric, and rogue.
Character roles identify which classes can stand in for each other. For example, if you don’t have a cleric in your party, a warlord serves just as well in the leader role.
Roles also serve as handy tools for building adventuring parties. It’s a good idea to cover each role with at least one character. If you have five or six players in your group, it’s best to double up on defender first, then striker. If you don’t have all the roles covered, that’s okay too—it just means that the characters need to compensate for the missing function.
Controllers deal with large numbers of enemies at the same time. They favor offense over defense, using powers that deal damage to multiple foes at once, as well as subtler powers that weaken, confuse, or delay their foes.
Defenders have the highest defenses in the game and good close-up offense. They are the party’s front-line combatants; wherever they’re standing, that’s where the action is. Defenders have abilities and powers that make it difficult for enemies to move past them or to ignore them in battle.
Leaders inspire, heal, and aid the other characters in an adventuring group. Leaders have good defenses, but their strength lies in powers that protect their companions and target specific foes for the party to concentrate on.
Clerics and warlords (and other leaders) encourage and motivate their adventuring companions, but just because they fill the leader role doesn’t mean they’re necessarily a group’s spokesperson or commander. The party leader—if the group has one—might as easily be a charismatic warlock or an authoritative paladin. Leaders (the role) fulfill their function through their mechanics; party leaders are born through roleplaying.
Strikers specialize in dealing high amounts of damage to a single target at a time. They have the most concentrated offense of any character in the game. Strikers rely on superior mobility, trickery, or magic to move around tough foes and single out the enemy they want to attack.