I see Roxas kinda being emo like Riku and keeping to himself (except Roxas has a better reason to be a loner), fighting the Heartless and possibly even the Nobodies on his own and only occasionally teaming up with the others. I also see Sora catching him off guard and bringing a smile to his face. He's be like Riku or King Mickey had he and Sora not merged. That's my thoughts at least.