Hello, I'm trying to use The Dude as a network monitor for an existing radio network.
Is this possible or do I have to create a server using RouterOS and connect the radios to that?

Thanks

Dude is usually installed on ROS, as it is stated in the documentation - System requirements for server package.

And next steps depends on how do you plan to collect the stats from your radio network. Mikrotik devices are natively supported, and for anything else you can use SNMP. In that way, devices should be reachable by Dude server.