Career
Born in Nijmegen, Janssen made his professional debut for VVV-Venlo in the 2004-2005 season, before signing for Roda JC in 2007. In November 2010, it was announced that Janssen would move to Football Club Twente at the end of the 2010-2011 season, on a free transfer. In August 2013, Janssen was sent on loan at Football Club Utrecht for the remainder of the season.