Thanks for the tip. I used LMS years ago when we had two Logitech audio devices. But after we didn't use them anymore I ditched LMS (it was also not anymore directly supported on a Synology NAS if I remember it correctly). But can LMS directly connect to a Denon AVC-X4800h AVR to play multi-channel FLAC-files?You may not necessarily need Roon endpoint functionality. I use Logitech Media Server (LMS), which is free. It connects to all of my devices, two of which include Roon functionality, but it connects via UPnP/DLNA. LMS also will stream via Chromecast, SlimProto, AIrplay, etc.
Give it a try. Like I said, it's free. So, if it doesn't work out for you, no money lost.