Collins played for Penn State from 1991-94, leading the team to an undefeated 1994 season.
Warren's announcement came after fellow tight end Theo Johnson announced his declaration for the NFL Draft.
Fashanu is a widely projected top-five pick.
Allen was previously a graduate assistant in Bloomington before his father's firing.
Hardy spent five years in Happy Valley.
Herron verbally committed to Penn State on December 11.