The process for attaching / detaching the DAC, managing the lifecycle of the USB driver, surfacing the correct info in the UI, integrating OS level volume controls, etc is totally different for the two apps since they do playback quite differently. I would say that these integration aspects took up 80% of the calendar for this project, and the USB driver development was the other 20%, so we are talking about a near doubling of effort to get both apps working.
Roon Remote only works at home. ARC works at home and on the go. The only significant gap is DSP, and we’ll close that with ARC as soon as we can, so it made sense for us to do this in ARC and let the Roon team focus on interesting stuff for Roon, instead of duplicating similar functionality that is already possible in ARC.