Hi Dan,
Providing some setup details will help the devs understand where any issue is arising.
As I understand it from guessing about your setup, your DAC is connected to your Core and you can now select it as a zone using the Core and it plays back. The DAC is not, however, appearing in the audio setup section of your iPad Remote. Any devices connected to the Core should be appearing in the Remote.
If, however, your DAC is connected to another Remote, and not to the Core, then your iPad Remote will not show it at the moment. That will be coming with RoonSpeakers.
Can you post screenshots of the audio setup screens on your Core and your iPad Remote ?