"We would like to welcome both Mike and Ron to the Silver and Black," Oakland general manager Reggie McKenzie said. "Both players are proven, productive professionals with excellent track records in this league. We are extremely excited to have them both play for the Raiders."
Bartell, 30, was limited to just one game last season due to a severe neck injury.
In 89 career games (65 starts) with the Rams, Bartell had 311 tackles and eight interceptions.
Brisiel comes to Oakland after spending six seasons with the Texans, where he played in 50 games (47 starts).
The Colorado State product was part of a unit that helped Arian Foster rank fifth in the NFL with 1,224 rushing yards in 2011.