Teams can free up to one (1) roster spot by
placing a injured player on Long-term Injured Reserve (LTIR) LINK.
http://www.profsl.com/smf/index.php?topic=8268.0* This will open up a roster spot but your team still bares the cap hit.
* Request can be processed at anytime, no specific dates for this and even applies through Summer (makes it slightly easier to manage from processing standpoint by leaving LTIR players in place).
NOTE: Understand that your player should be hurt and likely out for more than a few days otherwise we'll just remove the player from LTIR when they return from their gastro or sprained pinky!