I am running the Roon Android app on Kindle Fire HDX 7 (by downloading via browser and installing, works fine) as well as on pure Android devices (installation via Google Play Store). On the Kindle I see the same user interface as e.g. given by the Roon software on MacBook under OS X, so that the displayed items are rather small and difficult to interact with. On the pure Android devices I have a different user interface adapted to the smaller screen, similar to the IPhone app. This was also the case for the earlier version of the app.
Is the kind of user interface dependent on the screen resolution? As far as I know, the resolution of the Kindle is 1,920 x 1,200, for a 7" screen. It would be fine to have a switch for switching between the normal interface as I have currently and the optimized user interface optimized for handhelds.