The 26 year old penned a four-year contract at St Mary’s in August, completing a move from Brentford, but he has played just nine matches.
Denmark international Roerslev, who boasts a Championship promotion and 94 Premier League appearances, could boost Tonda Eckert.
The head coach had been without both Roerslev and compatriot Elias Jelert, although the latter has now returned and Roerslev could follow suit.
Eckert said: “It has taken a little bit longer than we were expecting it to take, but he’s due to join the group on Monday. We just need to take it day by day.
Southampton FC v Leicester City FC at St Mary’s Stadium. Tonda Eckert. (Image: Richard Crease)
“At the moment, it looks very good. We hope to have him involved very soon, but we’ll see how the next week goes. At the moment, things are very good.
“It is down to process. The players start individually before they get integrated into the team. He’s checked all of the tests that we do on the way.”
Midfielder Shea Charles is also set to return to training on Monday, following his setback from a hamstring injury initially sustained in October.
Oriol Romeu, 34, is yet to start a game for Saints since his sensational return in November, and he has been left out of Eckert’s recent match squads.
He could feature for Saints against Doncaster Rovers in the FA Cup third round, with Eckert adding: “We’ll see. We actually just had a conversation.
“He has looked good in training. We need to see what the best way is for him to get back to fitness, and for that, he just needs minutes.”