Countess was taken in the sixth round of the 2016 draft by the Eagles, who released the young defensive back in September of his rookie season. Countess was swiftly picked up by the Rams and then promoted to the club's active roster that November.

In three seasons as a Ram, Countess has appeared in 37 games and started in four. He moved from corner to safety in year two, where he recorded two interceptions, 25 tackles, and three passes defensed at the position.

Countess spent time as the primary kick returner in 2018. He fielded 17 kicks for an average of 24.6 yards per return.