Yes and no. There are a number of options from “proper” manufacturers that do just that (the Bryston BDPi is one example, it’s a RasPi with a HifiBerry hat, a screen, and a nice PSU, in a nice case with the appropriate warranty and retail markup (so over $1000).
Once you’ve gone through the expenses to make that happen, I’m not sure how much you make.
This said, there’s definitely space for a good industrial designer to make nice looking cases for the various Raspberry options, alongside easy to follow guides on how to snap 'em together. Sell case + a pre-burnt card, kick back the OS maker, and you probably have a business. The downside is you’re then in a business relationship with audiophiles, something I wouldn’t wish on my worst enemy.
I’m surprised as well. I’d wager Roon Ready-ness takes time and money. I’m even more surprised that the more progressive brands, let’s say Shiit and JDS Labs haven’t gotten in the nice Pi case business, and I’d guess there’s probably a very good reason to that.
You do have a few pre-built options (@ALLO_audio_boards and @Orchard_Audio come to mind), but the industrial design seems like the work of spastic two year olds, and the websites that sell them the endeavour of the four year old, on the spectrum, older brother. Clearly, nobody explained to whomever did those that normal people don’t know the difference between Volumio and DietPi, and, as they should, don’t care.
You’d need to licence the OS / rights to RoonServer from RoonLabs. Some have straight-up distributed ROCK illegally, and some (SGC and more recently Mytek come to mind, but there are others) have provided legal Roon Server options. They’re open to it, and it was one of the ideas behind ROCK.