Is the Roon/Rock showing up in the Synology Router (is it getting an IP address successfully)?
If no, can you connect a monitor to the HDMI on the NUC then reboot and see what happens?
If yes, Are the devices you are trying to connect to the Roon/Rock on the same subnet? Subnet is the first three numbers of the IP address (192.168.1.xx for example).
What devices have you tried to use to connect to the Rock. Which devices specifically are you having issues with?
The more information you can give the better for assistance.