Several CFL general managers were busy on Monday, adding new faces to their rosters.
Stafford, 29, has tallied 2,626 receiving yards and 18 touchdowns in 70 CFL games with Edmonton, the Montreal Alouettes, and the Calgary Stampeders.
In exchange, the Riders sent American kick returner Christion Jones to Edmonton.
Jones, 27, spent three seasons in Saskatchewan, returning 111 punts for 1,441 yards and three touchdowns, and 51 kickoff returns for 1,225 yards.
The Hamilton Tiger-Cats (5-2) also made a roster move on Monday, adding 25-year-old Canadian wide receiver Brian Jones to the practice roster.
Jones, a first-round pick by the Toronto Argonauts at the 2016 CFL draft, signed with the Ticats back in February and appeared in two games before he was released at the end of June.
He has 14 receptions for 148 yards and one touchdown in 36 regular-season CFL appearances for the Argos, Ticats and Saskatchewan Roughriders.
The Ottawa Redblacks also added a receiver on Monday, signing 23-year-old American receiver Micah Wright to the practice roster.
The Redblacks will visit the Edmonton Eskimos on Friday and the Riders will play in Montreal the same night.
The Ticats currently top the East Division standings and will be back in action on Saturday when they host the B.C. Lions.