Greg Eden scored a hat-trick as Rovers secured a vital 22-21 victory, which moved them above St Helens into seventh. The visitors had been trailing 13-12 at half-time after they raced to a 12-0 advantage, but Michael Dobson's touchline conversion five minutes from time following Eden's third score clinched a win which edged them closer to the play-offs.
"We are all frustrated after that and disappointed to lose," Frayssinous said. "In the end I have to ask the question 'did we deserve to lose or did we deserve to win?' And if you look at the game as a whole, there are some good signs and some bad signs."
He added: "Defensively we were pretty good. On the other side, we didn't do enough to win, but we have to move on."
Frayssinous refused to directly blame the officials for their handling of the game, with the Dragons having three tries disallowed by the video referee and Rovers being awarded a controversial first try.
"You know the rules of the game like me, and you, me and everybody here made his own opinion of the decisions," Frayssinous said. "Rugby league rules are simple rules - unlike rugby union. Their rules are pretty complicated. It's up to everyone to make their own opinion to the no tries or tries."
Hull KR coach Craig Sandercock was delighted with his side's performance, and he said: "It's pleasing and I'm happy for the boys. They tried really hard and, although we weren't at our best, they never gave up and I'm more happy for the boys than anything else.
"It was a really entertaining game that seemed to fly by, but those last five minutes were probably the slowest five minutes of my life. That's rugby league."
The game was staged at Toulouse's Stade Ernest Wallon with the French side looking to promote rugby league outside of their Perpignan base, and Sandercock was full of praise for the venue.
"I think the ground and the atmosphere helped the game," he said. "The ground is absolutely impeccable and we love playing on a dry surface and I'm pretty sure Catalans do too, and I think that added to the spectacle."