At the anniversary event they only let slip Red Mage and Samurai. That with the info they have said in the past about 3 being to many leads me to believe we will only get Red and Sam.

Now as to their roles, the realist in me says Sam will be a tank and Red a dps. But the creative and OCD part of me sees Sam as a dps sure, but Red as a tank. Why?

Because Red Mage is traditionally a jack of all and master of none, which in this game is a tank. Tanks can self heal... sort of, and dps... sort of, and tank. The other two roles can at times but only tanks are given skills and stances allowing for shifting play. I know I will throw a Clemency at a healer in an emergency, and off tanking is basically weak dps. Also as mentioned, my OCD (not just saying, diagnosed) Black Mage - dps, White Mage - healer, Red Mage - Tank.... that would ease my mind.