Let's say Scottie Pippen knees don't allow him to play this year. So he retires, the Bulls still pay him $5M this year and the Bulls carry another 15 players on their roster.
Question is: Can the Bulls include Pippen in a trade? Or does he need to stay on the 15-man roster?
I'm pretty sure that Pippen would have to be on the 15 player roster in order to be traded.
Unsigned rookies are another case altogether. Teams hold their rights until they sign and can trade those rights. But once a player is dropped off the 15 player roster (waived, retired, etc.) the team loses all rights to him.