Salas, 27, is a former fourth-round pick of the Rams back in back in 2011. He lasted just a little over a year before he was traded to the Patriots in return for a seventh-round pick.
Since then, Salas has played for the Eagles and Jets before the Lions brought him in on a one-year contract back in May. Detroit wound up placing him on season-ending injured reserve with a knee injury and later releasing him with a settlement a few weeks into the season.
However, the Bills eventually signed him to a contract towards the end of December.
In 2015, Salas appeared in two games and recorded three receptions for 41 yards receiving and no touchdowns.
Gillislee, 25, was a fifth-round pick of the Dolphins in the 2013 NFL Draft. He spent just over two years in Miami before he was among their roster cuts at the start of the regular season.
After a brief sting with the Cardinals, the Bills signed him to their practice squad before promoting him to their active roster close to a month ago.
In 2015, Gillislee appeared in five games and ran for 267 yards on 47 carries (5.7 YPC) to go along with six receptions for 29 yards receiving and three total touchdowns.