TB, I usually agree with you, but not in this case. I've never bought this opinion that there was competition between Neri and Rocco. Neri was clearly Michael's Majordomo, his Luca (per the novel). Rocco was a capo, apparently Michael's only capo in Nevada. Neri had no need to push past anyone. He was already at the head of the line. Tom was only selectively utiized by Michael. He asked Rocco about Roth since it would be Rocco's manpower that would carry out the murder.

Neri, Tom, and Rocco were the subordinates that Michael had at his disposal. As such, whatever action they took would, of course, be interpreted as at Michael's behest by those who were in a position to know such things.