Twin brother of fellow Rover Martin, Markus also started out at local Swedish side Högaborgs BK. Both brothers came over to Lancashire for a trial back in the winter of 2005, and whilst Martin secured a permanent move to Rovers, Marcus returned to Sweden to further his footballing career.
2008 saw Olsson make the move to top-flight club Halmstads BK where he would go on to make 139 appearances, scoring on 17 occasions during four-year spell.
Earlier this month he earned his first caps at international level, featuring for Sweden on two occasions as they played friendly matches against Bahrain and Qatar.
Olsson has signed a two-and-a-half year deal with Rovers that sees him contracted until the summer of 2014.