It remains to be seen how classes will unfold here in EQ2 as compared to EQ1. If they are ANYTHING alike, then we may see the following: (From quick memory of classes, might miss some new ones)
Warrior/Berserker - Meat Shield, Tank for the most part. DPS
Shadowknight/Paladin - MA in groups, SA/DPS in raids.
Monk/Bruiser - DPS (possible tank in EQ2, but I doubt it)
Templar/Inquisitor - Healer, buffer
Warden/Fury - Healer, nuker, utility
Mystic/Defiler - Healer, Mob debuffer, utility
Wizard/Warlock - Nuke DPS, Crowd Control
Illusionist/Coercer - Crowd Control, Buffer
Conjurer/Necromancer - Pet class DPS, Crowd Control
Ranger/Assassin - High DPS, Limited Crowd Control
Swashbuckler/Brigand - DPS, ???
Troubadour/Dirge - Group Buff/Mob Debuff, Crowd Control, DPS
It shall be seen, given time, how these classes unfold and what they find rolls for.