I also have an audiointerface with many analog and digital (SPDIF, optical & coax) outputs. However I am not able to feed even one of these outputs into Roon in a good (i.e. lossless) quality (see the remark below). How did you manage to make it run with one stereo channel?
Remark: It works for me with a somehow complicated setup, however the audio quality is not exciting. I have connected 2 outputs (currently I use analog channels but want to use SPDIFs in future) of the audiointerface (i.e. a stereo signal) with 2 inputs of the same audiointerface. The audiointerface (it is an Apogee Ensemble Thunderbolt) is connected to an Apple Mac mini. With the application Butt (https://danielnoethen.de) the audio signal is streamed to an Icecast server application (icecast.org), both running on the same Mac. The Roon core server is currently (I have ordered a Roon Nucleus+ but it will be delivered only in April) also running on the same Mac. Within Roon I have set up the Icecast server as an Internet Radio station. With this setup I am able to stream one stereo output of the audio interface to Roon audio outputs. The same setup would in principle also work with more than one stereo channel and several radio stations, as long the audiointerface has enough outputs and inputs of the same kind. Since Roon (and maybe also the other involved software) currently only supports Internet Radio connections with MP3 and AAC, the audio quality is limited. The best quality which can be achieved is: stereo, 44.1 kHz, 16 bit, AAC with 320 kbps.