FFC may have taken liberties with what we Board members know about Mafia SOP. The main one for me is that Roth didn't have any troops. So, who was he going to turn to to execute Michael? Well, Ola, right? But it's never clear just who Ola is and his Mafia hierarchy standing. I always took him to be a capo. Unless he's a Don himself, Roth had to get the okay from at least one Don to take Michael out, right?. I would think that he would have needed more than one Don given Michael's preeminent position in the underworld. And Roth aligning himself with (just) a crew in the Rosato brothers does not rise to the level of what we probably figured to be Roth's level of intelligence and logic.
I believe Roth was thinking and acting out of the "Mafia box." I think he planned to have his pals in the Cuban government's intelligence organization (called SIM) assassinate Michael and the soldiers in the military car that was taking him back to his hotel, making it look like Michael accidentally got caught between the government and the rebels.
I also don't think he needed permission from any Dons to whack Michael, who was by that time posing as "legitimate," and was far away in Nevada (and Havana). In fact, the birthday party was designed by Roth to create an alibi for Michael's assassination ("Hey, it wasn't me--I loved the kid. Just ask all those guys at my birthday party"); and to line up support. He promised shares of his territories to other Mobsters at the time of his retirement or death--the rest to Michael. With Michael out of the way, there'd be more for them to share.
