Some colleges do post their fall rosters and you may see as many as 40-41 on the fall roster. By the official spring roster they must be down to 35 total, including red shirt players.
Of those 35 only 25 will make the travel roster which may change from game to game.
And the players also have to remain academically eligible to be on the roster. It is a tough business! These kids work harder than they ever have in their lives to juggle classes, studying, working out, practicing, and a little social life! As difficult as it seems they wouldn't be there if they didn't love it.