Rivers has a spot on the Rams' initial 53-man roster, Stu Jackson of the official team website reports.
The Rams kept both Rivers and Zach Evans behind Cam Akers and Kyren Williams. They won't necessarily stick with four RBs throughout the season, so either Rivers or Evans could be sent to the practice squad in the coming days/weeks. Rivers bounced between the practice squad and active roster as an undrafted rookie last year, playing 25 snaps on offense and 36 snaps on special teams in eight games for the Rams.