With Jimmy Garoppolo and Trey Lance cemented as the Niners' top two quarterbacks and veteran Nate Sudfeld outplaying Rosen in the battle for a possible third spot on the depth chart, Rosen became expendable when San Francisco claimed cornerback Davontae Harris from the Baltimore Ravens on waivers.
Thus ends a relatively short stint with the 49ers for Rosen, who never appeared in a regular-season game for the team after it signed him from the Tampa Bay Buccaneers' practice squad on Dec. 23, 2020. The 49ers re-signed Rosen on Feb. 8 in hopes he could push for the No. 3 job, but Rosen's struggles in camp mounted over the past couple of weeks.
"I think he started off real well," coach Kyle Shanahan said on Aug. 8. "I think he's taken a couple of steps back the last few practices. You know, it was unfortunate on that. We were supposed to go to someone and we had a busted route, so then it kind of fell apart and he tried to overcompensate and he made a bad situation worse."
Rosen, 24, played most of the second half in last week's preseason opener against the Kansas City Chiefs, going 10-of-15 for 93 yards with an interception in a 19-16 loss. After the game, Rosen spoke of how much he liked playing in Shanahan's system but noted the difficulties in getting into a rhythm when you aren't getting as many reps as the top two quarterbacks.
"It's been a pleasure," Rosen said. "I really look forward to coming to work every day and Kyle is a brilliant offensive coordinator/head coach. ... Just coming to work every day, it's really fun playing football. I like playing for these guys, I like playing with this team. So, in general, it's very positive, I've had a lot of fun."
The Arizona Cardinals originally selected Rosen with the 10th pick in the 2018 NFL draft out of UCLA. He was traded to the Miami Dolphins the following year and then landed on the Buccaneers' practice squad on Sept. 8, 2020. The 49ers signed him to their active roster in December following injuries to Garoppolo and backup Nick Mullens.