Rocco was promoted to take Paulie's place in the family after Paulie betrayed the Don. He was promoted by clemenza. In the book he is the one who shoots Paulie in the car with Clemenza shortly after the Don had been shot. This is shown in the movie too, but not sure if the movie shows Rocco or someone else shooting Paulie. Hope this helps. This was my first post!!!
VITO CORLEONE (to Johnny, after glancing to see Sonny enter)
You spend time with your family?
JOHNNY
Sure I do.
VITO CORLEONE (to Johnny, but toward and about Sonny)
Good. 'Cause a man who doesn't spend time with his family can never be a real man.
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