Will Roxas come back to the Kingdom Hearts series

Sorta. He has already become one with Sora. At the end of KH2, as you know, Sora and his friends get a letter from King Mickey. The letter is about KH3: Birth by Sleep. In the game, one of the main characters looks ALOT like Roxas. He isn't really Roxas, and you still play as Sora. I'm not 100% sure about what the exact storyline is so if you want, google it.