This does not affect the Islanders salary floor situation. According to Capgeek, the Isles are able to shed 7.7 million in salary (either in trades or waivers) without taking any salary back and still be above the floor.  In this case, promoting David Ullstrom does add some prorated salary back anyway, and Rolston has a 35+ contract which counts against the cap even if he is waived.  The only way for the salary not to count would be if another team claims him, which is unlikely.  Scroll down the page to see the salary floor teams.