Michael saying Carlo grew up in Nevada and moving him up once he became boss was a ploy keeping the enemies close
He was going to be whacked, he had to answer for Santino

Rocco's status changed after killing Paulie He became part of the family He was eating dinner with them before Sollozzo and McCluskey killings

I think it is fleshed out in the book Clemenza said something like he would be looked after once all these problems were taken care of by the family