He fills the vacancy created by waiving Tillery:

Daniel Popper @danielrpopper

Chargers have signed RB Larry Rountree to the active roster [from the
practice squad] and elevated K Cameron Dicker and OT Foster Sarell from
the practice squad [for the 49ers game].

3:14 PM · Nov 12, 2022

Here are the Chargers' recent transactions:

Nov. 12: Signed RB Larry Rountree to the active roster from the practice
squad

Nov. 10: Waived DL Jerry Tillery

Nov. 9: Signed DL Christopher Hinton and OT Austen Pleasants to the
practice squad.

Nov. 9: Placed DL Austin Johnson (knee) on IR and signed DL Breiden
Fehoko to the active roster from the practice squad

Nov. 5: Placed TE Donald Parham (hamstring) on IR and signed WR Keelan
Doss to the active roster from the practice squad.

Nov. 3: Signed K Cameron Dicker to practice squad. K Taylor Bertolet,
who has been filling in for the injured Dustin Hopkins, has been placed
on the practice squad injured list.

--Robin