The third-year quarterback hooked up with Jeremiah Johnson, Bryan Burnham and Marco Iannuzzi before giving way to backup Travis Lulay just before halftime.
Lulay then delivered a 12-yard TD toss to Emmanuel Arceneaux in the third quarter, while Loucheiz Purifoy added a defensive touchdown on a fumble return.
Jennings finished 10-of-14 for 197 yards, looking cool and collected in his 28 minutes of action after a bit of a slow start. Swayze Waters was perfect on five converts for B.C., while Ty Long kicked seven points.
Josh Stanford had a touchdown for the visitors, while Tyler Crapigna had a field goal and Quinn Van Gylswyk added an extra point.
Kevin Glenn started at quarterback for the Roughriders and played the first quarter in his exhibition debut, going 5-of-7 for 81 yards, including an 41-yard completion to Duron Carter. Glenn is in his third stint with the Roughriders after playing for the club from 2001 to 2003 and again in 2015.
The Lions lost their pre-season opener in Calgary against the Stampeders 23-18 on June 6, while the Roughriders tied the Winnipeg Blue Bombers 25-25 in the first game at the new Mosaic Stadium in Regina last Saturday.
With the exhibition schedule now down, CFL teams have to declare their 46-man rosters on Saturday, meaning it will be a nervous night for players on the bubble.
The Roughriders open the regular season schedule on the road Thursday against the Montreal Alouettes. The Lions kick off two days later when the Edmonton Eskimos visit Vancouver.
Trailing 3-1 after the first quarter following Crapigna’s field goal, B.C. efficiently moved the ball on a drive that was capped by Jennings scrambling out of trouble to find Johnson from 11 yards out for an 8-3 edge.
After getting stopped on third down at the two-yard line on their next drive, the Lions got the ball back in Saskatchewan territory, with Jennings finding Burnham from nine yards out for a 15-3 advantage.
Iannuzzi then got in on the action after a Saskatchewan turnover, hauling in a 33-yard TD from Jennings to make it 22-3 at the break as the Lions’ explosive offence, which was minus free-agent speedster Chris Williams as he continues to recover from an anterior cruciate ligament tear suffered last season, looked to be in mid-season form.
Lions defensive back Anthony Thompson, in a battle to start at corner, dropped a sure touchdown on a bobbled interception off a throw from Canadian quarterback Brandon Bridge early in the third quarter, something B.C. saw far too much of last season when the club finished with just nine picks _ by far the fewest in the league.
But T.J. Lee, who tore his Achilles last July, would make amends for the secondary by intercepting Bridge later in the quarter to set up Arceneaux’s TD catch that made it 29-3.
Purifoy, who would also add a late pick, then forced a fumble by Thomas Mayo and returned it 37 yards for a touchdown on the final play of the quarter to make it 36-3.
Bryan Bennett, Saskatchewan’s third quarterback of the night, got the Roughriders a little closer when he found Stanford on a 39-yard TD midway through the fourth.
Long responded from an early missed field goal to connect from 49 and 42 yards out put the Lions up 42-10.
B.C. is coming off a 12-6 campaign where the club won a playoff game for the first time in five years and Jennings cemented himself as a star by becoming just the fourth quarterback in franchise history to throw for more than 5,000 yards.
Saskatchewan is set to begin its second season under head coach and general manager Chris Jones after going 5-13 in 2016. The Roughriders will be looking to get back to the playoffs for the first time since 2014 after going a combined 8-28 the last two years.
The Lions’ defence is going to see a lot of new faces in 2017 with half the starters from last year having moved on. Standout linebacker Adam Bighill is the biggest name to leave the unit that led the CFL in the fewest yards allowed after bolting for the NFL’s New Orleans Saints, while veteran defensive back Ryan Phillips was released before signing with the Montreal Alouettes.