Fighter
1) His role is to fight. Whenever the answer to a problem is fighting, he goes in first, without hesitation, and never worries about whether he has the skills to engage the enemy. He stands at the toes of dragons, he wades into platoons of orcs, and he hurls an axe when a goblin sneak threatens the wizard. His mastery is managing the position of the enemy, ensuring they cannot atack his allies without becoming vulnerable, while causing them damage, round after round.
2) His power source is courage and training. Fighters do not fear to melee with an ogre, because they have confidence in their skills.
3) A fighter uses his mastery of the tools of war: armor, weapons, tactics. Some fighters are deadly with anything they put in their hand, others specialize and become the unquestioned master of a preferred weapon. Heavy armor is not mandatory, but if they aren't heavily armored, they choose some other type of defense that is also effective, such as a strong parry, unarmored grace, or indomitible toughness. Fighters are smart, but rarely academic or courtly; even King Arthur's knights were basically jocks.
Rogue
1) His role is scouting, detecting, acquisition, and ambush. Whether in a town, in a dungeon, or on an alien plane, the rogue takes point whenever a fight isn't going on, but there is a danger of one. In combat, he is active, but does not simply beat on the monsters; he maneuvers, harasses, and delivers sudden, surprise attacks. He might attack a monster to keep it off a weaker party member, but once he has its attention (if it isn't dead), he tricks it into losing situational advantages.
2) His power source is training and courage, with a little luck. Like fighters, rogues are not afraid to dive into what they've been trained to do.
3) Rogues are plucky, agile, and sneaky. They are always ready for action, sleeping with a dagger under the pillow, fighting effectively if ambushed in an alley in town, or filching something valuable they happen to see. They are effective talkers, not inspiring, but very convincing. A rogue should no incentive to put on heavier armor unless he is some kind of multiclass character.
Cleric
1) The cleric's role is to fortify the party, participating in battles, casting spells that help them overcome obstacles, and tending to the wounded and shaken. Some clerics, especially evil ones, instead weaken the enemy, performing deadly attacks and cursing foes. The cleric is always right behind someone else, aiding the fighter in melee, preparing a rogue with protective magic, or defending a wizard so he can cast a vital spell. The cleric is asked to display extraordinary courage and to wade in when other characters need to retreat. While a helper, they are not merely an assistant but a savior.
2) A cleric's power source is belief, fortified with divine power and magicla study.
3) Clerics are in the midst of trouble, always, and tend to wear heavier armor or at least use a shield or protective spell because of that. Unless they are some kind of multiclass character, their combat abilities are second-rate, but they are effective with a variety of weapons, typically more common ones or ones associated with their deity, culture, or philosophy; for instance, a nature cleric might use a bow, a war cleric might use a sword or spear, a deity of healing or mercy might use a mace rather than carry an overtly aggressive sword, and a secretive cultist uses a dagger, shortsword, or sickle. Clerics are at home in their culture, whether tending the woods and wild places, participating in a church hiearchy, or reporting to an order of divine crusaders. They have a serenity and gravity that lends itself to diplomacy, intimidation, and requests for aid. They embody moral forces of the universe, and have a strong connection to things that are evil or good, unnatural or natural, and so forth.
Wizard
1) The wizard's role is to create wonders. A wonder is something rare and special. The wizard can unleash a powerful spell, incinerating several foes that seemed almost unbeatable moments before. They can conjure things as needed, overcome obstacles, and create unusual solutions to problems. When confronted with a river to cross, a wizard might cause his companions to fly, turn them into ducks, turn the river into firm earth, or conjure a bridge, depending on his knowledge of spells. Other party members protect the wizard so his spells will be available when their potency is needed.
2) his power source is magic, controlled through training and will
3) Wizards, unless multiclassed, are not well-versed in combat. However, they have the skills of adventurers, and are often talened with a handful of weapons and special options, as befits anyone who has had a goblin try to skewer him more than once. Archetypally, they do not wear armor, instead depending on spells and prudence. Wizards are mysterious and knowledgeable. They do not treat magic frivalously. A wizard strives for power, saving his spells for when needed, seeking out new knowledge, and almost greedily seeking out new magic items. A wizards's demeanor sets him apart from ordinary people; perhaps he wears a special costume, but even if he does not, the tools of his trade and his sagely knowledge make him impressive. Mutliclassed wizards, although somewhat less potent, perform tasks in a wondrous way; wizard-rogues turn invisible, then practice impossible stealth, cleric-wizards can solve almost any problem with a spell or miracle if needed, fighter-wizards deliver amazing attacks or combinations of spells and ability.
