I read the varying opinions on this with interest but have made my choices and thought to share my experience.
When I switched from Sooloos to Roon nearly 5 years ago I chose a (used) 12" iPad as the remote and still have it. But, as others have commented, it can seem too large for purpose at times and it has frustrating limitations for editing. So, deciding on getting another remote to use for a different room, I finally decided on a used iPad Mini 5. I chose the 5 rather than the 4 as most available used units are less than 2 years old so have a better potential battery etc life.The screen size is perfect for general use.
I’m no great fan of Apple despite cutting my teeth on computers with an Apple IIe decades ago. They are overpriced new but the displays are superior so have a thumbs up from me. And the Mini5 is fine for basic remote ROON use for me.
That said I’m finding I’m using a M/S Surface 2 more and more away from the PC which houses ROON. The notebook is perfect for minor editing, something which continually crops up with the large classical library here and its larger hi-rez screen is better for reading attached pdf files.
More serious editing is performed on the main PC screen with a Samsung 32" screen.