There are several topic on this if you search on opengl or on server 2012.
Bottom line:
- you need to run an opengl driver
- remote desktop does not allow that
Workarounds:
- use splashtop
- or start roon using a batch job on your headless computer. It logs you off, starts roon and when you connect a little later you can then use remote desktop just fine.
I use the latter option.
the script (from: Install for Roon on Intel NUC + Win2012R2 Essentials - Using Audiophile Optimzer):
tscon.exe %SESSIONNAME% /v /dest:console
timeout 1
Start C:\Users\Administrator\AppData\Local\Roon\Application\Roon.exe