I just recently upgraded to win 10 64 rocksmith2014 was working after the upgrade but the windows coruptdates kicked in and I was stuck. UBI support was no help after messing around I have come across a fix that might help anyone still having issues and win 10 and it is fairly easy.
Simple fix was to go to C:\Programs Files(x86) and move the steam folder to the root of C:
make sure you do not have compatibility mode or administrator mode on and simply launch it from steam. This worked for me.
Unfortunately It took me a few weeks to figure this out and only by a little luck and some trial and error.
I hope this helps and good luck
