Well, I’m running the Roonserver and it installs and run in signs-in user profile.
So logs are located here C:\Users[userprofile]\AppData\Local\RoonServer\Logs
But I guess you are running Roonrock on your NUC, which I believe runs as a service so log files would be at a different location. I would guess something like
C:\Program Files\RoonRock\Logs
C:\ProgramData\RoonRock\Logs
C:\Program Files\RoonServer\Logs
C:\ProgramData\RoonServer\Logs
But just guessing…