Fiammetta recently was moved from the reserve/left squad list to the active roster. He spent the entire 2012 regular season on the reserve/left squad list after signing with the team as a free agent last offseason.
Herman was signed as an undrafted free agent last year, but suffered an Achilles' injury that kept him out for his entire rookie season.
Robertson was signed to the team's practice squad late last season, then signed a reserve/future contract following the season.
Williams, a 2011 seventh-round draft choice, moved between the active roster and practice squad in 2012, playing primarily in a special teams role.