Williams, 25, is a former third-round pick of the Chargers back in 2013. He was in the final year of his four-year, $2.353 million rookie contract and set to make a base salary of $675,000 for the 2016 season when he was cut loose coming out of the preseason.
The Rams signed him to a contract a few weeks ago.
In 2015, Williams appeared in 13 games for the Chargers and recorded 19 tackles, one sack, two interceptions, two forced fumbles, a recovery and five pass defenses.
Johnson, 24, originally signed on with the Lions as an undrafted free agent out of Georgia Tech back in May of last year. He lasted just a few months in Detroit before he was waived and later signed to the Lions’ practice squad.
Detroit once again elected to cut Johnson coming out of the preseason and he later caught on with the Rams and signed to their practice squad.
In 2015, Johnson appeared in two games for the Lions and recorded two tackles.