Messam is set to enter his fifth CFL season, after originally entering the league in 2010 with the BC Lions.
After one season in B.C., the 29-year-old was traded to Edmonton where he amassed 1,057 yards rushing on his way to being named 2011 CFL Most Outstanding Canadian and League All-Star.
The Toronto native attended Miami Dolphins training camp in 2012 before returning to Edmonton for the remainder of the season. He was traded to the Montreal Alouettes ahead of the 2013 season.
For his career, Messam has totaled 1,882 yards rushing and 11 touchdowns on 381 carries while adding 698 receiving yards on 71 catches. He has played 59 regular season games.
The Riders also announced the addition of international defensive back Ciante Evans to the teams practice roster.
Evans (5’11 – 190) joins the Riders after spending four seasons with the University of Nebraska Cornhuskers. The Texas native started 33 of 48 career games posting 143 defensive tackles, 19 pass knockdowns, 15 tackles for loss, five quarterback sacks and five interceptions.
The 21-year-old was named First Team All-Big Ten in 2012 and 2013.