My first time posting something like this!
So I was asked to solo Alysrazor for a friend so he could get Do a Barrel Roll.
I pulled and he stood on the side doing nothing and he didnt touch the boss at all, just AFK'd on the side and let the boss kill him. Then when the boss died he could roll on the drops but didnt get saved! Should work for any boss I guess.
All you need to do is not attacking a boss but be present during the pull!
Just delete if its a repost, I couldnt find anything about it so I posted.
Pce.
Edit: Tried it today and apparently it was just a bug in my friends calendar not showing he got saved. Sorry.