Hi !
To continue the reply of Jody, i think this is a real important question ,and Joe Morley's advises in his method are also very interesting too, but ,...if you are looking on Vess Ossman or Van Eps music scores, you will find some differents fingerings and differents ways to pick alternative motions of right hand fingers, mainly on Van Eps music.
As a lover of Ossman and Van Eps music and interpretations i learned the differents pickings used by them, Fred Van Eps was playing only forward rolls, thumb, index, middle, in any case he was NEVER changing this motion, if you can heard about his interview by Lew Green, he is speaking about this T.I.M. motion, and he say that he is able to play about 14 notes per second, for me i am only using the Van Eps fingering.