The 27 year old defender came off with the injury which has now been assessed and Rosler was remaining tight lipped on Barnett's expected absence.
However he did reveal that the former Nowich defender hasn't been ruled out for the season.
Rosler told the Wigan Evening Post: "Leon has been assessed, and we know what he has done and roughly how long he will be out.
"All I will say is he is not out for the season. It is a blow, especially because of the way Leon and Emmerson Boyce were linking up with each other.
"When you have that solid spine, you want to keep the continuity. But we are blessed in that department."
Barnett has joined a growing Wigan Athletic injury list with Ben Watson, Chris McCann, and Roger Espinoza all recently injured.
Ivan Ramis is expected to take Barnett's pace for tonight's game with Yeovil.