HS and College pitcher prep for starter or closer

In high school you may not be using a dedicated closer. You may also have limited pitching depth. What I always had was a staff that worked hard, each and every kid the same way. Then we as a coaching staff, chose our starters and based on schedule, can expand or contract the starters. All of the other pitchers essentially become relievers. By late season you'll know who you have the most confidence in late in the game.
College coaches that I know will work the same way, but many big time staffs search out and create different bullpen slots and closers as well.
As for regiment, maybe one of the college coaches can answer that for you.

PitchDad,

I am currently taking part in these preseason workouts. I do not have the best arm stamina so I figure maybe short relief to hopefully a closer role. We all throw the same, work ourselves up to 75-90 pitches. This is also on a 5 day rotation the first two weeks and then it turns into a 4 day rotation the last three. Some players have certain injuries that may set them back.

This year I struggled with shoulder tendonitis so I only worked up to 60 pitches. We have yet to define roles on our team outside of the starters for the first 3 games, but I am sure other schools may plan different.