The Roughriders (10-8) finished third in the West Division and will travel to Edmonton next Sunday to face the Eskimos (12-6) in the West semifinal. It'll be the fourth time in the past seven weeks these teams will have met. The winner will face the host Calgary Stampeders in the West final the following week.
The Eskimos hold a 2-1 advantage in the head-to-head divisional series.
It was the first win for Saskatchewan since Joseph joined the team nearly a month ago and just the second win for the Riders since quarterback Darian Durant was injured on Sept. 7.
Tino Sunseri relieved Joseph to start the second half and promptly threw a 40-yard touchdown pass to Rob Bagg to give the Riders a 23-4 lead. Sunseri completed both of his pass attempts for 59 yards. Bagg had three catches for 65 yards.
Korey Williams had an 18-yard run for a touchdown in the first half for Saskatchewan. The Riders churned out more than 200 yards rushing on the night, led by Anthony Allen's 81 yards.
Having already locked up second place in the division and a home playoff game, the Eskimos did not dress quarterback Mike Reilly, running back John White and receiver Adarius Bowman. Matt Nichols started in place of Reilly and threw for 240 yards, rushed for a touchdown and was intercepted twice.
Hugh O'Neill kicked three field goals for Edmonton, including two in the second half. The Eskimos' lone touchdown came late in the fourth quarter on a two-yard run by Nichols. The score was set up by a fumble recovery inside Saskatchewan's five-yard line.
John Chick finished the regular season with a league-high 15 sacks. He was the first Riders player since Vince Goldsmith in 1983 to lead the CFL in that category.