https://www.horizonmb.com/
install this app
insert a flash drive that has a roster save from the 360 on it
open the horizon app, device explorer pane on right-side should list what's on the flash drive
navigate to the game save, expand tree for nhl15, where you should see the name of the roster save that you made from within nhl15 (360)
double-click on the roster save, then in right-most tab (contents I believe), it should list the roster save with a timestamp, right click on this, choose replace, choose the db file (NOT THE ZIP FILE) that I attached in these threads. Confirm you received a confirmation prompt
choose the "Save and Rehash" tab (second tab), confirm with OK prompt
close Horizon, eject/remove your flash drive, insert into 360 and load within the game