My take, for what it is worth!

Everything was amicable in Roth and Michael's father / son alliance! Johnny Ola assured Michael at Anthony's party -

Extracts:
“The casino you're interested in.....I've been instructed to tell you that if you move Klingman out, our friend in Miami, Roth the real owner [with the old Lakeville Road group from Cleveland] will go along”

Michael: “That is very kind of him. You tell him, that's greatly appreciated”

Nobody suspected any foul play Michael himself didn't even twig straight away that it was Roth who tried to kill Michael in his Tahoe home

How Rocco and Neri “would have been right on Roth's ass if Michael had been killed, demanding their cut” [what cut?!] even if “they were probably going to have a part in Michael's planned takeover [what takeover?! Michael was Roth's heir apparent!] of Roth's Havana properties”?

Besides everything was work in progress and with Batista gone, Roth's empire like Roth's birthday cake! was gone too Nothing left to carve up for anybody's cut