Interesting. Possible. But I doubt it. A liklier scenario, IMO:
Congressional committees schedule hearings months in advance, the better to enable members to milk the publicity value. Roth would have heard about the Mafia hearings and would have been concerned that the hearings might involve him one way or another. He'd also have heard that Questadt was "for sale." So, I'm figuring, he bribed Questadt handomely to keep him informed.
Roth was in Cuba when the Frankie garroting went down, and probably didn't hear that it failed--he was busy with other things, and had a stroke. But Questadt learned about Frankie's survival immediately through his contacts in the NYC police with whom he'd been working on the Mafia investigation. BING! Questadt saw dollar signs.
As you say, Klydon, he was sharp. He immediately hatched the perjury trap. He convinced the committee chair that he and his fellow Senators could get famous by using Frankie to trap Michael. He convinced the chairman to lean on the FBI and the NYC police to keep Frankie's survival secret and turn him over to the Feds. Meanwhile, Roth had escaped Cuba and recovered from his stroke and attempted assassination. Alerted about Frankie's survival by Questadt, Roth fed him incriminating evidence on Michael and anything else he knew, including the famous brothel murder that implicated Senator Geary, a member of the committee.
Geary was the key player. Questadt would work the brothel-murder angle to get Questadt to trap Michael. Questadt would tell Geary: “Here’s your chance to get revenge on Michael Corleone.” The unspoken threat: “I know about that brothel murder—if you don’t go along, you’ll be exposed.” It seems to me that this complex plot would work far better if Questadt were informed about it and on board. Withholding it from him would be very risky--he'd be pissed about being left out, and might even be tempted to tip off Michael in return.