Red Mage: (Tank) Ideally, I think this would only work as a tank. The White Mage, Black Mage, and Red Mage represent an ancient trinity in the Final Fantasy franchise. FFXIV has a trinity as well, the Gaming Trinity of the Tank, Healer, and Damage Dealer. As White Mage and Black Mage fit well into two of those roles, Red Mage would be left the role of a Tank. How does a Red Mage tank? Using iconic Red Mage abilities. The en-element spells to generate aggro and inflict status conditions upon enemies. Abilities like Phalanx to reduce damage, Blink to increase evasion, lengthy self-heal buffs to increase survivability, etc... With heavy reliance upon Parry as a form of damage mitigation, much as Blocking exists for Paladin. Its not ideal and doesn't fit the Red Mage thematic 100%, but it's the best we can hope for.

Blue Mage: (DPS) I can't really see this as anything other than a DPS to be honest. It certainly has some utility in other games, and it can bring utility to FFXIV, but in the gaming trinity, it'd fall into a DPS more than a Healer or a Tank.

Samurai: (DPS) I don't see this being anything other than a DPS given Yoshi P's comments. That, and I'd like to see another armored DPS like Dragoon.

Dancer: (Healer) A melee, DoW healer would be a refreshing change of pace, especially if we get a DoM tank in the Red Mage. Using combo's and perhaps abilities which place debuffs on enemies which heal party members who strike said enemy.

Beastmaster: (DPS) A melee DPS for certain. Ever since I saw those tigers added, I've been wondering when they'd add this class. It'd be interesting to see a Whip as a weapon as well. Sort of the DoW version of a Summoner, I imagine. A melee, dot-laying DPS with a pet.