I think this anxiety thing is overblown. Flying in the NBA is like riding in luxury, you hop on a private charter that is plush inside and being that a lot of the flights are late night you'll sit down and fall asleep after a game probably. It's not like he'll have to go through airport security and wait at the terminal like you would for a commercial flight which from what I have read the pre-flight stuff is what gets his anxiety going and he's fine once he's in the air.
Anyone who gets Royce in the 20's is getting a steal. Everyone keeps referring to him as top 10 talent then there is the "but..." followed but the anxiety disorder stuff. As much traveling as he'll have to do in the NBA it won't take long for it to just become part of his routine and seem like nothing. In college he had to fly maybe once a week, twice at most. In the NBA he might be flying 3 or 4 times a week if they are on a long road game stretch.