For me I went for Han so I can pair him up with Jonin Minato. His ability to remove buff is great especially when you fight against heavy buff teams like lightning blitz. Han overall is pretty good and can really change the fight depending on the type of lineup you go against, also the fact that he can't be comboed is a plus. The only thing as of right now that I can say is bad for Han is the fact that he is not immune to status effects like Roshi so he can easily be cced. Roshi on the other hand is pretty much a cheaper 4 Tail Kyuubi Naruto who can chase and has a mystery that hits up to 9 units and removes barrier. The only real problem I've seen with Roshi is the fact that his chase requires 30 combo and that kind of limits you to certain ninjas and summons if you want to pull off his chase. When it comes down to it they both are really good, and of course they have their own flaws. The biggest thing is to decide based on the ninjas you have/plan to have or what kind of style you prefer to play.