Sure like to help but i’m kinda busy and this is not really the forum to talk docker stuff.
So good you guys figured out that you have to map stuff.
Also you need to add host networking (only do that for containers you trust) instead of bridging so roon can easily reach your devices.
Basically when you would have set up the container with a command like mentioned on the docker hub page thats done for you (but when using the synology gui you ll find the options too)
docker run -d
–net=host
-e TZ=“Europe/Amsterdam”
-v roon-app:/app
-v roon-data:/data
-v roon-music:/music
-v roon-backups:/backup
steefdebruijn/docker-roonserver:latest