To be honest, if you're not going to use any functionalities of Windows other than playing Royals, then no. Activating or not doesn't have a difference. I have a few VMs with Windows on it, and I don't have them activated. Also, it's really...really dumb to have Windows activated in a VM environment, or at least that's in my opinion...
Simple googling showed me this: i.e. the pop up that you'll have to live with, and perhaps other stuffs like antivirus (but you can live without them...just get those free ones like Avast or what not).