As others gave said, it’s officially completely unsupported by Roon.
But if you have a fairly decent understanding of networking, routers and VPNs you can get it to work.
You’ll need to be running a VPN like Wireguard to connect back to the Core. But you’ll also need to use an additional UDP proxy like udp-proxy-2020 to send UDP broadcast packets over different subnets so that your remote clients / endpoints can be discovered by your Core.
Have a read of the following, or search for VPN.
But unless it all makes clear technical sense to you and/or you have exactly the same setup / hardware as one of the guides below, it’s probably best to skip trying to get it to work. Getting Roon to work over a VPN is very much in the ‘tinkering’ category for now.
If you don’t understand what your doing there is a real chance you could brick your router or cause yourself no end of headaches. So tread carefully.