In addition or instead of moving the control linkage (and you might already know this) you can execute a much faster and prettier roll by using rudder and elevator. Airspeed helped rolls on my trainer too.

Also, moving the cg back will help roll response and all other response too. Just be careful if you do this. Make sure you do some reading first.

Another thing, it looks pretty bad but I saw a guy extend the ailerons on his trainer by using balsa sheeting glued to the existing aileron. So the aileron was no longer 1.5" wide, but like 3" wide. Granted it looked bad, but WOW! I'd never believed a trainer would roll like that! This is kind of a brut force method though.