I doubt that Roth knew Frankie had survived until Roth recovered from his stroke. Here's how I think it went down:
--Frankie started talking trash about Michael as soon as he revived. NYPD, recognizing that they finally had on their hands a Mob higher-up willing to rat out his boss, kept Frankie's survival secret, to keep him talking and to protect him from others trying to finish the job the Rosatos started.
--Questadt, Roth's man, was chief counsel to a Senate committee looking into organized crime. He had contacts in NYPD. They told him immediately about Frankie's survival. BINGO! Questadt had a brainstorm: he convinced his committee chairman to get NYPD to release Frankie to FBI custody so the committee could use him to set up Michael for the perjury rap.
--Questadt then contacted Roth. Roth was surprised that Frankie survived. But he immediately figured that if he hadn't known that Frankie was alive, neither would Michael. He then supplied Questadt with details of Michael's involvement in the Great Massacre of 1955, nationwide gambling, etc. That info became the source of the questions the Senators and Questadt asked Michael at the hearing, that set him up for perjury.
--The FBI told Cicci that Frankie had survived and was going to testify against Michael. They advised him that, since his boss was willing to break omerta, Cicci had nothing to lose by doing likewise. If he did, he'd get a break, like Frankie did. If he didn't, Cicci would be the fall guy. Cicci went along.
--The beauty part here: Neither Frankie nor Cicci realized that Roth was pulling the strings! Michael himself didn't realize it until Fredo told him: "That Senate lawyer, Questadt--he belongs to Roth."

As for Vincenzo: the look on his face is one of astonishment that his brother was about to break omerta. But he also could have been worried about the consequences on him and his family at the same time.