I think you need the Poly to make that Mojo its own endpoint, visible as such in Roon, otherwise its the iOS device you are streaming to: you won’t see the Mojo as an option in Roon Endpoints. Which of course is significantly more expensive than a camera connection kit. 
Although that looks like it might have issues of its own that may or may not be worked out on the Chord side of the implementation looking at this old thread.