The 24-year-old full-back moved to Griffin Park from Manchester City in 2011 and has played in every league game this season.
Rosler told the Bees' website: "This season Shaleum has been more consistent than last year.
"He has played nearly all the games in a very demanding position and he has earned this 18-month contract
"He is still young enough to improve and we are delighted to have him on board.
"Everyone wants to be part of a successful team and I am delighted that players and staff are committing themselves."
- Sports & Recreation