Roon uses several TCP ports, and some UDP too, and makes connections in both directions from server to remote. It uses a variable number of ports depending on how you have your system configured.
A huge part of it is about isolating different kinds of work from each other on different protocols that are optimized for each task. Audio streaming is a real-time operation that’s about ensuring constant throughput and predictable behavior. Driving a remote control is about delivering bursts of data rapidly in response to user interaction, and artwork loading is handled asynchronously in a best-effort manner. Each requires separate attention and isolation from the others.
One idea that has been floated is for us to assign ports out of a fixed range of perhaps 1000 ports, that way you could configure forwarding for that range.
I think the next step here is for you to explain your setup in more detail. What are you doing, what are you trying to accomplish with this stuff, etc. Maybe there’s something we can do to make setups like yours more viable, or maybe there’s something we could recommend as a way to work around these limitations.