Vanitas is a Jerk. That is Roxas's mantra and probably won't be changing anytime soon.

The fact that they're actually having/had a civil conversation right now is honestly surprising. But it's sort of giving Roxas a new perspective on Vanitas. He's still a jerk, but perhaps not as big of a jerk? At the same time, Roxas won't hold his breath and there'll be hell to pay if Vanitas does anything to that ice cream pokemon.

So yeah, Vanitas is a jerk and Roxas has a one-track mind.