Leroux, 26, is a native of Montreal and made his Major League debut with Florida last year on May 26. He made a total of five appearances with the Marlins in 2009 and spent and majority of the season with Double-A Jacksonville, where he posted a 2.70 ERA and two saves in 46 games.
A seventh-round selection by Florida in the 2005 First-Year Player Draft, Leroux made his professional debut in 2006. He also appeared in two games for Team Canada during the 2009 World Baseball Classic, tossing 1.2 scoreless innings.
To make room for Leroux on the 40-man roster, the club has designated right-handed pitcher Brian Bass for assignment.