The Raiders announced three transactions on Thursday afternoon.
Teamer became a free agent when he was cut by the Colts last month. He never played a game for Indianapolis as he signed with the team in January.
He did not play in 2020 after being cut by the Chargers. In seven games for Los Angeles in 2019, Teamer had 40 tackles, an interception and a sack.
Magnuson made one appearance for the Raiders in each of the last two seasons. Williams played basketball in college and signed with the Raiders in April.