NFL rosters should be 60 players.

53 is more than enough to field a team on Sundays, there is no justifiable reason for 60 players on a team. Just let them all dress and be eligible to play.

The roster is flexible during the season - the team you begin the season with is not the one you need to end with, and IR takes care of replacing injured players. The owners don't care, there is just no reason to do it.