Since 2016, it appears that many small internet radio services have ended up removing their public free streams apparently due to the loss of lower royalty rates for small service providers. The end result is while they continue to maintain and mobile web applications, some seem to have turned to subscription based services that embed a user specific access key in the stream URL.
Some of these services (DI.FM and the associated family of stations for Jazz, rock, classical etc) maintain many sub genre specific channels that are just painful to manually maintain through the existing UI, but however share a simple and common enough model that could be trivially handle through a simple Roon extension if API support was there.
As it seems from https://community.roonlabs.com/t/roons-new-internet-radio-directory-curators-wanted/74319 that Internet radio is getting a facelift, then a way in which Roon could provide for easy user consumption of such subscription services would be through extending the Roon node SDK to allow for import and management of groups of radio stations, allowing interested users, or perhaps even the actual service providers themselves to provide simple extensions to give an appropriate user experience.
For eg, with DI.FM (and their companion stations), one could write simple web app that could perhaps extract or provide all the channel metadata and icons following their service URL pattern and import them into Roon. Perhaps as new channels get added by the service, they could be automatically noticed by such an extension and made available for the user to add to Roon as a favourite radio, but with the users private stream key included in the URL.
I think that in the context of Roon’s internet radio getting a facelift, such SDK support could be a means to provide a great and possibly unique user experience for dealing with subscription based radio services.
I only mention DI.FM in this because I have a subscription with them that also covers their other stations (for jazz, classical, rock etc) and that tends to be my main use of internet radio. However they have hundreds of channels and manually managing these in Roon today is painful 
There may even be opportunity with such an extension for some degree of minor commercial partnership/affiliation with such services, for eg, if a service provider web extension was included in Roon and provided a means of discovering channels and starting a subscription through Roon.