Troubleshooting networks remains a dark art to me.
One thing that plagued my network for awhile: a network loop. It created an enormous amount of excess traffic.
There are network gurus around here, but your job one is to tell them your network setup: hardware, wiring, who’s connected to what.
I’ve never had a network bandwidth problem. There’s more than enough bandwidth for Roon and others. If you’re trying to do things on the same machine as the Roon core, then I would say you are CPU bound, rather than network bound.
Improper setting of managed switch options drives Roon mad. Best not to attempt.
Can you let me know the model/manufacturer of all your networking gear and how everything is connected? I would also suggest that you take a look at our Networking Best Practices Guide for any useful suggestions there.
I have a very busy network and never any issues, even to wireless endpoints. I would say if your runnig core on a general purpose computer that you use for other things then its likely the culprit. Also if you are using wireless for the core and endpoints then this will but a big drain on your wireless network. Wireless unlike wired is not duplexd so up/down traffic comes out of your overall wireless throughout which for domestic routers and access points is not always great.
I found the Mini and especially macOS to be not quite up to the task.
To further my point about bandwidth and machine juice; sometimes I play a movie thru Plex with the sound down and select appropriate music to play in Roon.
All on the same i5 and thru the same switches, FWIW.