Since he referenced a 91 as needing 7 parts, and he did not post in the clone forum, the presumption is HK German guns, so my answer would be zero parts. Must be a trick question.
I’d imagine that the OP is looking to make a SBR from a original German gun, so he needs to make it 922r compliant. The 5.56 roller locks should be the same as the 7.62 versions, which I believe need 7 parts. The 9mms need one less because they normally don’t come with a muzzle device.