Hi Susan,
Roon will be able to see your B2 as a NAS but other than that I cannot currently see a way to integrate a B2 with Roon.
This is because the only inputs for audio content the B2 has are its HDD , SD card, USB drive (if connected)., aux input, and Spotify Connect enabled by Librespot.
I’m not sure that Roon can take Spotify as an input and anyway it uses its own app to enhance and control how content is rendered.
This is quite a good article on how Roon works
John