Rivers amassed 310 yards, connecting with Malcolm Floyd seven times for 127 yards and a touchdown, while finding Antonio Gates with five passes for 106 yards and a score.
The Chargers (8-8) finished the season with four wins in five games.
The Raiders (8-8) lost for fourth time in five games and came up short in their bid to make the playoffs for the first time since 2002. They needed a win to take the AFC West title outright, but Denver, which also lost Sunday, took the crown in a tie-breaker.
Carson Palmer went 28-of-43 through the air for 417 yards with two touchdowns and an interception for Oakland.