You are absolutely correct TB, and here is some evidence to back it up:

1. "Keep your enemies closer" - Michael goes out of his way to get Roth's permission to move Klingman out, and Roth dispaches Johnny Ola and his men to Tahoe to give the go ahead. Michael is very solicitous of them, offering the men food, etc., and listening to Ola praise Roth as the last of the old timers, and a man who always made money for his partners. Of course Roth gave the go ahead because he thought Michael would be dead in 24 hours. After the hit, the first person he visits is Roth to ask permission to kill Pentangeli. Roth, who now thinks Michael is way off base tells him what a wise young man he is, and Michael replies by saying how much he can learn from him.

2. Corleone family scuttlebutt - The two times Michael gets skunked in arguments in the trilogy, he shuts up and changes the subject. The first was when he was trying to put pressure on Moe Green for slaping Fredo around. When Michael is told this was because Fredo was banging cocktail waitresses two at a time, he knows his point is lost and he just gets up and says that Green should think about a price. The second is during the argument with Pentangeli in Tahoe. Michael tries to convince Frankie to go along with his plans by telling him how Vito respected Roth and did business with Roth. Pentangeli trumps him by saying yes but he never "trusted" Roth. Again, Michael's point is lost and he simply lets Frankie leave. If Frankie knew Vito never trustd Roth, Michael had to know the same thing, and he also didnt trust Roth. This is proven by Michael's comment about Roth dyng of the same heart attack for 20 years. Micheal knew full well of this ruse long before the hit on him but he just played along with it.

3. Ola's Call To Fredo - Even after Michael visits Roth, the plan to kill Michael is still moving forward. Ola calls Fredo to see if Pentangeli is realy going to make the deal with the Rosatos. In other words ROth is fishing to determine the sincerity of Michael during his visit to Miami.

4. Michael's intelligence gathering. I dont know exactly how Micheal learned that the plan was to have Batista's soldiers kill Michael after the New Year's party, but learn it he did, and he had to dig pretty deep into his resources to learn that the plot to kill him was still on. Incidentally this harkens back to the insight Michael had about Sollozzo...that the key for him was to "kill pop." Likewise he got proof that the key for Roth was to kill Michael.

5. Roth's arrogance. By the time of the birthday scene Roth smells a rat. He doesn't know Michael has fgured out how he is to be assassinated, but when he takes Michael aside after Michael makes his "Castro could win" comment. He clearly expresses his displeasure and growing impatience with Michael.
Later, when Michael shows his hand by asking who ordered Pentangeli killed, Roth is furious. In the great scene in which Roth praises Moe Green he makes the point that more than anyone in his life he "loved" Moe Green, and yet he never mad inquiries because it was business, not personal. Roth knew very well who gave the order to kill Moe Green, and at the end of that speech he issues a direct threat to Michael. Either the money is on the table or he knows he doesn't have a partner. He might as well have told Michael he would rub him out.

6. Fredo's continued silence - After Michael "forgives" Fredo at Mama's funeral, Fredo stays on the compund but he keeps to himself. He never discloses that he knows Pentangeli is alive, or that the Senate lawyer is on Roth's payroll. Even when everything blows up at the committee hearing he lies to Tom Hagen and says he knows nothing, yet when Michael confronts him, he tells Michael he knows Pentangeli is alive and "they've got him" and that the Senate Lawyer belongs to Roth. I have argued this before, I think Fredo did know it was going to be a hit, and he did know Roth's motives. I think we have a consensus that Fredo opened the drapes, so he had to know. Still he continued to lie to Michael about it.
Why? I think Roth promised Fredo he would be head of the Corleone family after Michael's assassination. That was the "something in it for me." It would rectify Fredo's being passed over. And btw it is the reason Michael was right to kill him.