johnny rotella played on a two first albums by the mothers of invention. he also contributed to zappa's "lumpy gravy", and later to "the grand wazoo".
info from charles ulrich:
he apparently drummed on one don & dewey track. as for why he wasn't on the grand wazoo tour, remember that one of the questions kenny shroyer asked was "are you free to travel?" rotella probably wanted to stay in la and do sessions.
if rotella played on absolutely free, i think it would have been the contrabass clarinet on "brown shoes don't make it".
discography - with frank zappa and / or the mothers of invention
mothers: the grand wazoo
(1972, lp, usa, bizarre)