Ask the coach. Different schools have different philosophies on rosters. When we were going through the recruiting process, we asked every coach how many kids they would bring in during the fall and everyone answered truthfully. One school said they only bring in 35. I have checked their fall roster the past couple of years and they only list 35 players. Most said they will have 40-42 players in the fall. Players will get hurt. Players will become academically ineligible and some will not develop and will be redshirted and some kids will quit or move on to another school.
During sons last fall playing showcase, he played a tournament at a top 10 program. Sons team was playing the first game of the night and the school was playing a scrimmage. They had 52 players in uniform and another 4 or 5 walking around in shorts. This school hasn't posted a fall roster for the past 3 years either.