Rae found him living in a swamp in Louisiana, a homeless man whom the local authorities were trying to catch and take into protective custody. She was in the area droping off Desmond for his Negotiator training, and a news story about him catches her attention. He's sort of a local legend. Leroy apparently had been living ferrel for a very long time and could easily elude people trying to capture him. He was not able to communicate with normal people, but Rae goes out there with her HomeWorld Air car, waits for him to come to her, and then gets permission to take him home with her to HomeWorld and marries him, and takes care of him for the rest of his life. He is still with her at the time Jason stays with them, although his is not in good health. He gives Jason the Guitar he made for Desmond which Desmond never played, and then teaches him to play it. He probably knew when he made it that he was going to give it to Jason, and that Desmond would not use it.
Desmond and Leroy never got along well. Desmond accepted the guitar when it was given to him, and kept it in his office on HomeStation, almost never played it because the uncanny ability it had to accurately express the feelings of whomever played it made him very uncomfortable. Jonathan Landon plays it once in the Chapter where he is introduced in "History of Paragnagia". Desmond returns the Guitar to Leroy when he knows he is going to die before Jason is born and tell Leroy to give it to Jason for him.
By the time Jason is going to Paragangia Leroy is no longer alive but I don't remember when or how he dies