I am using my desktop machine as a remote to my music server.
The server works fine, the remote also, but Roon does not see the local audio devices.
They disappeared couple month ago.
I was waiting if a Roon or Windows update will fix the issue but it has been the same. (Windows 10 Pro 1709 (16299.19))
I also uninstalled / reinstalled Roon but no luck. (Currently the latest is installed)
I had to turn off all firewalls (domain and local) that did not help.
After that I restored the original settings for all firewalls and when I started Roon it asked for permission and started to work with local audio devices.