Johnson suffered a shoulder injury in a Week 6 loss to the San Francisco 49ers.
Johnson's setback is the latest in a string of recent injuries for the 3-3 Rams.
Each team can activate only two players from IR.
A third-year pro, Johnson has two interceptions this season. He will be replaced by backup safety Marqui Christian.
Troy Hill will replace Talib, and on Wednesday the Rams expect the arrival of cornerback Jalen Ramsey after trading a 2020 and 2021 first-round pick and a 2021 fourth-round pick to the Jacksonville Jaguars.