Technically, there is no limit on the number of players that can be on a college football team.'
However, FBS programs are limited to 85 scholarship players. Any additional players on the roster must be walk-ons.
Division I FCS programs are limited to 63 scholarships. Unlike FBS programs, though, FCS teams can award partial scholarships to players. In theory, 85 FCS players could split 63 scholarships.
There have been recent proposals that would cap the number of total players allowed to appear on a roster, which would essentially be a limit to the number of walk-ons a team could take. For now, though, those proposals have not been made into official rules.