I wouldn't say a large amount, they were still a minority. Hitler was born a Catholic, with his mother being devout, but his writings evidence that he was quite skeptical about it and his actions definitely so.

Goebbels was also born Catholic - he even was considering going to seminary to become a priest. However, he went on to writing and philosophy, though he wasn't very successful there, and went to politics.

Himmler was born Catholic as well, but, just as with Hitler, his writings show us that he eventually became quite anti-Catholic and actually very much anti--Christian in general.

Rudolf Hess' story is very similar to Goebbels', though it seems that while in prison after the war, he re-professed his faith and received sacraments.

I can't think of any other prominent members with a Catholic background, but I'm sure you can see that all of them were not Catholics in any sense by the time they were in power. Catholicism in general was heavily persecuted in the Third Reich, despite the promises of the Reichskonkordat.