Saturday’s 1-0 win away to Swansea means Forster has still not conceded since he returned to the side from a long-term knee injury.
He and Saints are now one game away from tying the club record for consecutive clean sheets in the top flight, set by Paul Jones 15 years ago.
“I think Fraser is one of the best in the league for sure and even in Europe,” Romeu told reporters after Saints fifth victory in their last six.
“Fraser deserves all the compliments, but also the defensive line, the midfield line, the offensive line, it's teamwork and I think we are doing a very good job.
“Fraser has saved us many times, but I think the three at the back they have been perfect, in the crosses, in every one-v-one. The team performance defensively has been perfect in the last games and that's why we are keeping those clean sheets.”
On the victory at the Liberty Stadium, which lifted Saints to sixth in the Barclays Premier League, Romeu said: "It was a very important win. It was a battle, it was a tough game. We did well scoring that goal, Shane Long getting that header into the net, so very happy, three very important points and another clean sheet.
"Even more the way we defended, the way we played, I think we were very solid all game, and the last five or six games has been the same. We have that mentality, that team shape, so it's very good to keep doing this. We are very happy and very proud of our team.
"We are in a good position and we fought a lot to get up to here, so we have to make sure we keep doing the same things, because the teams behind us are going to try to get that place and they're going to fight to go higher in the league also. So we have to be ready.”