The California alum was a 2013 fifth round draft pick of the San Diego Chargers. Williams missed his rookie season due to a pectoral injury. He finished his two playing seasons in San Diego with 29 tackles, 2 interceptions, 1 sack and 2 forced fumbles.
To open up a roster spot for Williams, rookie linebacker Nicholas Grigsby was waived.
Additionally, the Rams signed offensive lineman David Arkin to the practice squad and terminated the contract of practice squad running back Terrance Magee.
Williams will wear No. 41.