After Update on Roon 2.0 on the Windows PC I can not see the headphone and my USB loudspeaker. Under “Audio” connected to Core I can only select a device with “ALSA” and “HDA Intel PCH HDMI0”. Before updating all worked perfectly. On my notebook in the same network all works fine.
As a test, try turning off the Firewall on the Win 11 PC and see if the audio endpoints appear. If they do, then you need to add exceptions for roon.exe and raatserver.exe. Faq here.
If they still are not appearing, you might also check the firewall on the Qnap.