Polygamy - I still maintain a UPnP server on the same Library as Roon, for my NDS.
The Roon route is through a SonoreUPnP Bridge, which runs on an UltraRendu/UltraCap LPS 1
So the UPnP server is redundancy in case any part of the Roon based playback path fails.
Also the nature of UPnP support on the Naim NDS network player is as a Pull based Render - the Naim App, requests Library details and content from the UPnP server.
Roon is a Push to Endpoint model.
They presently co-exist, and Roon is used as the Primary interface.