When youre running Romans offense, you need a ton of people to hand the ball to. They may not need to bring in 9 WRs to camp like other teams that throw alot more, but they need backs in camp to learn the playbook. It isnt uncommon to have 2 or 3 backs dinged up at one time, so why not use him as the primary PR (as a safe option) and have him ready to take a few carries if the rest of them get hurt?
A one yr veteran deal makes sense if youre getting someone who can carry multiple hats into camp.