check your engine mount, those tower trainers are clamp mounted and it may have come loose and is shifting in flight.
if your plane can all of a sudden roll faster, that will have little to do with the stab (which looks fine btw), unless the stab is shifting in flight (can you move it around? does it feel different than before). im guessing that your engine is flopping around so when you turn right the engine shifts right thus pulling your plane to the right more than usual.....right? [8D]

or maybe your battery is loose and shifting around in the fuse, or your wing is shifting.

did the plane fly fine for a little while then all of a sudden start acting up? or were you fighting it the instant it took off?