Sa, 22, makes the move as part of an agreement which sees Dragons forward Jason Ryles go the other way, with both players having two years left on their previous contracts.
Dragons Football manager Christophe Levy said: “Following the capture of Dallas Johnson, I am very pleased to sign another Test player with Setaimata SA. He will be a big asset to our attacking line. He had 2 years left to his contract with the Roosters but I think we found a fair agreement between the 2 clubs by releasing Jason Ryles to them.
“Since the creation of the club we have been very pleased with the recruitment of the Kiwis players. Stacey Jones and Alex Chan have been great ambassadors of our club in the world. Setaimata is still very young but we expect as much from him.”
Johnson was signed from Melbourne this week in what is seen as a major coup for the French side, who finished 8th in Super League last season but made it to within 80 minutes of the Grand Final, losing to eventual winners Leeds.
He said: “I have enjoyed my time playing in the NRL for the Sydney Roosters and have been lucky enough to have the opportunity to represent New Zealand. I am now very excited about the opportunity to play overseas for the Catalan Dragons and am looking at this move as a new and exciting challenge for my family and I.”
His versatility will prove a big asset to coach Kevin Walters, with him able to cover in the centre, back row and at stand-off.
Former Brisbane assistant Walters said: “I am very excited to have secured the services of young New Zealand player Setamaina Sa. Although Sa has had a difficult season with the Sydney Roosters he is very much looking forward to arriving and playing for the Dragons in 2010/2011.He is a big ,strong and skillfull backrower or centre with tremendous potential.”
Catalans will find out on Wednesday their opponents in next season’s Magic Weekend. The full Super League fixture list will also be available on the same day, November 18.