Boldin caught five passes, including a 20-yarder for the 49ers’ first score.
He ended up with 90 receiving yards from Colin Kaepernick, who also hit Vernon Davis for a score.
San Francisco led 14-3 at the half and padded it to 21-3 when Kaepernick hit Davis on a 12-yard score with 8:53 left in the third quarter.
The 49ers improved to 2-2 while the Rams dropped to 1-3.
Frank Gore also rushed for 153 yards and a score for San Francisco.
In the third quarter, St. Louis lost starting safety T.J. McDonald to a leg injury. Trainers immediately put an air cast on McDonald’s right leg, and he was carted off.
STEELERS: Running back Isaac Redman told the Pittsburgh Post-Gazette that he returned to a Sept. 16 game at Cincinnati despite suffering a concussion at the beginning of it.
Redman said he told Steelers doctors he was “all right” so he could get back into the game.
The Steelers have disputed Redman’s claim and said the team followed NFL-mandated guidelines for players who may have suffered a concussion.
RAIDERS: Terrelle Pryor returned to the practice field three days after sustaining a concussion but is not participating in team drills.
Pryor was in uniform Thursday and took part in stretching but did not have a helmet and mostly watched backup quarterbacks Matt Flynn and Matt McGloin run practice during the portion open to the media.
Pryor was knocked out of Monday night’s loss in Denver in the fourth quarter and did not practice Wednesday. Pryor has said it would be difficult to start Sunday’s game against Washington if he did not practice Thursday.
REDSKINS: Quarterback Robert Griffin III knows there’s someone in town who might be able to help him with his sliding.
“I mean, if Bryce (Harper) wants to do that, I’m definitely up for that,” Griffin said. “Bryce, we can do that if you want to, buddy.”
Harper will have some extra time on his hands after the Washington Nationals’ season ends Sunday.
But even the 20-year-old phenom might not provide enough help in teaching Griffin how to do the one thing his coaches want him to do more of this season: get low and avoid big hits.