Jason Armstead signed as a free agent with the Ottawa Renegads on September 16, 2003. Armstead didn't see any actiion until 2004 when he had a strong rookie season, seeing action both as a wide receiver and returning kicks. Armstead had 41 catches for 608 yards and added 700 yards on kickoff returns and 821 yards on punt returns including one 91 yard return for a touchdown. In 2005, Armstead had a superb season as a pass receiver with 89 catches for 1307 yards to win both East and CFL All-Star selections. Armstead also had over a thousand yards in kickoff returns and 699 yards on punt returns with another touchdown on a 87 yard return.
When the Renegades failed just prior to the start of the 2006 season, Armstead was selected by the Saskatchewan Roughriders in the dispersal draft and reunited with Ottawa QB Kerry Joseph. Armstead got off to a good start with the Riders, but faded as the year went on and ended up with 47 catches for 651 yards. Armstead was also used in an "end arond" play quite a bit with the Riders that year with 19 carries. In 2007, the Riders used Armstead mainly as a kick returner and he had just 15 catches in 8 games before he was traded to the Hamilton Tiger-Cats for former Rider Corey Holmes and Canadian receiver Chris Getzlaf.
The Tiger-Cats were desperate for receivers and Armstead got more action with 31 catches in his 10 games with the Cats. 2007 was a so so season for Armstead as a kick returner. He did have his third punt return for a touchdown, a 90 effort, with the Riders before the trade but didn't do much with Hamilton, averaging only 5.0 yards on punt returns. Hamilton released Armstead and he signed with Montreal for the start of the 2008 season, but lasted only four games.The Als used Armstead almost exclusively as a kcik returner as he had just two pass receptions. As a kick returner, Armstead didn't have his former razzle and dazzle and he was released.
Armstead signed wih the Winipeg Blue Bombers where he played 10 games, being used exclusively on kick returns where the speedy Armstead got his game back on track with 795 yardss on kickoff returns and 624 on punt returns including an 84 yard return for his fourth career punt return touchdown.
Armstead returned to the Saskatchewan Roughriders for 2009, playing ten games and again almost exclusviely as a kick returner. Armstead helped give the Rider return game some spark with 806 yards on kickoff returns and 387 on punt returns. In the off season before the 2010 season, Saskatchewan signed free agent kick returner Dominique Dorsey and it looked like Armstead would have a stiff battle on his hands at training camp to retain his kick return job, if the Riders decided to keep him until camp. In April, 2010, Armstead simplified the decisoin for the Riders when he ran into trouble with the law in Mississippi over theft charges involving his former girlfriends' car, and Saskatchewan released him.
That incident seemed to finish Armstead's CFL career, but Armstead seemed to instead become a "hired gun" for teams needing a kick returner due to injuries. In 2010, Edmonton found themselves short a a kick returner and put out the call to Armstead, Armstead returned to Edmonton in 2011 and then in 2012 when Larry Taylor was injured, Armstead was picked up by the Calgary Stampedres. Armstead was released by Calgary in February, 2013.