These are the ports I have open on my Roon Core VM:
TCP: 9330:9339,30000:30009
UDP: 9003,32768:65535
I stream to my Uniti Atom and a Chromecast device and with these opened up I’m not having any issues.
Roon isn’t very forthcoming with the info on the ports.
They give this post Roon Api on Build 880: Connection refused error :( - #15 by Geoff_Coupe as an explanation but it just seems to me as an excuse to use whatever random port they can pull out of their hat without any prior notice.