There is no Web UI for Roon Server on any supported OS. The Web UI is part of the OS and thus only available for the Nucleus(+) hardware from Roon Labs (that comes with it’s own Linux based OS) or devices that run ROCK (a slightly modified version of the OS used on the Nucleus(+) that enables users to build their own Nucleus(+)-like appliances).
If you really need/want to use your NAS for directly ripping CDs then the Roon Extension: CD Ripper looks like a way you can try.