I mean at this point the basics have been explained thrice over and the goalposts are being moved I'd suggest just getting started and seeing where you get to
You'd be better off just getting on with using it instead of worrying about whether you'd rather live in a world where you had two applications instead of one 🙂
There's nothing stopping you from calling Roslyn just as there's nothing stopping you from calling rustc. It's just much more common to use the build tools (dotnet and cargo).