The 22-year-old midfielder helped his side to the Ligue 2 title last season but found his opportunities limited towards the end of the campaign - reportedly due to his impending departure.
And the former West Ham boss admitted that it may take time for his latest acquisition to reach his peak again, but backed him to acclimatise to the Premier League.
"Romain's a player who has been off the radar for a while, so it's going to take him some time to get back to his very, very best," he told Chronicle Live.
"However, he is coming into a great environment and I'm sure he'll settle very quickly. That's the beauty of the French market.
"He plays across the midfield, a bit like Sylvain Marveaux."
The 50-year-old also revealed that the club's recent success means they will have no trouble in persuading players to join their ranks.
"Word of mouth is very good and there's a lot of contact from players wanting to come to this club," he added.
"That arms me for the Europa League and it well help me to bring players in and out."