The moves leave the Bills with just 50 players on the roster, giving them three roster spots to fill before they reach the 53-player maximum.
Scott, 32, notched 66 tackles and intercepted four passes in 16 games (one start) for Buffalo in 2012 and has been a key reserve in recent seasons.
Troup was the Bills’ second-round pick in 2010.
Buffalo traded for Lewis six days ago after quarterback Kevin Kolb suffered a concussion in the club’s third preseason game. The Bills now have just two quarterbacks on the roster: first-round pick E.J. Manuel and undrafted free agent Jeff Tuel. Manuel is recovering from knee surgery.