This company makes a set of physical controls (buttons, disks, sliders) that can be combined in various ways. Mostly for Adobe products, but it’s adaptable, I’m sure it could be extended for Roon.
It is aimed at professional products where you spend a lot of time and prize productivity. Not really a Roon thing, I prefer the relaxed iPad experience. But physical, analog controls do have an appeal…
EDIT I just noticed on their site, they list built in support for “iTunes, Spotify, WMP, VLC“