Last season, the midfielder made 25 Super League appearances, scoring twice as Pedro Martins’ men finished third.
After completing the move, Romao has urged the club’s fans not to relent on their support for the team which propelled the side to win the Ligue 2 and secure promotion to the top-flight.
“I followed what the club did last season, I saw the fan's backing - now we are in Ligue 1, there will surely be more difficult times and we will really need their support," Romao club website.
"If we have less good periods and we see that the fans are behind and do not let go, it pushes us to make even more effort.
"We are ready to do the best for next season to be successful.”