"Anyone with a DIII kid out there?"
My son is a returning D3 player (will be a junior this year).
At his college, there was no document signed formalizing the verbal agreement that he would play baseball there or receive a spot on the roster. His initial commitment was made to the head coach in one of their periodic phone calls, and then the coach followed it up with a letter welcoming him to their program, saying they were excited to have him on board, etc.
Technically there are open tryouts in the Fall, but the coach doesn't expect to see any surprise, non-invited recruits show up. If they are serious about playing for the program, they have had significant contact, have made a visit to the school, and in most cases the coach has made a trip out to see the player in a game situation - or at least he has gotten as much info as possible about the player from some other coach he trusts. I did hear of one walk-on (two years older than my son) who made the team without ever having talked with the coach before setting foot on campus, and became a starter by his junior year.
This year the total roster will expand to 46 players and a JV team will be added. All 46 players will compete in the Fall to determine which roster they make, varsity or JV, and all positions are considered open for competition, even those held by returning starters. But my understanding is that the 46 known players will all receive a spot on one of the rosters as long as they meet all of the team expectations and fulfill the academic requirements.
That's just the way it is done at one D3 school...