My two cents worth!

Rocco failed to secure Tahoe Why would Michael trust him bodyguarding Michael, Kay and the children, again

No doubt Neri seemed like he was closer to the business side and he leads the discussion near the end about Roth's prospects for avoiding arrest
He was the special assassin, chosen to kill Fredo, was told in advance too, not knowing when the mother will die

So, why was it Rocco not Neri or Tom presenting papers for Michael to sign, witnessing so personal children are outside we're going

Any significance in Rocco's presence