The Bills signed Johnson to the 53-man roster Friday.
He had resided on the Bills' practice squad prior to the transaction, while fellow running back Damien Harris (concussion/neck) was placed on injured reserve in a corresponding move. Johnson will provide depth in a Buffalo backfield that also includes James Cook and Latavius Murray. The running back out of Maryland has appeared in 62 NFL games and has a career average of 4.4 yards per carry.