I believe you’re asking about a product called rooExtend. rooExtend is a collection of licensable Roon extensions - you install rooExtend on a Pi and purchase licenses for the capabilities you want to enable (and some capabilities, though not dial control) are free. Surface Dial support is one of the extensions. There’s also a turnkey hardware option available.
The relevant threads are:
If you want to go the turnkey hardware route, instead of a Pi, that information is here: