If you have found yourself trying to add or remove a feature on Windows Server 2012 R2 and an error, The operation cannot be completed, because the server that you specified requires a restart, but you know it doesn't need a restart, have a look on this post, it shows how to fix that.
Issue:
If you are facing this issue on Windows Server 2012 R2 when you are trying to add or remove a feature:
And you have already rebooted the Windows 10 times at least and nothing; do the following action.
How to fix it
Enable the service "Remote Registry"; set it up as "Automatic" and then start it.
After to enable and start this service, you will be able to successfully add your Role or Feature.
For any doubts or suggestions, please leave a comment below.