I have digital music folders in my Nucleus that include sfv, nfo, and m3u files, are they useful to Roon or would it be better to delete them and save space?
These files most likely originate from a download source, with… their own interpretation of copyright .
Sfv files are used as a tool, to determine whether your download is intact or not. If the file you received, is exactly the one that the uploader had provided. It serves no purpose within Roon.
Nfo files, are actually txt text files, and contain human-readable information on the content of the download. Also has no use in Roon.
M3u files, are playlists. In Roon, they should appear as a playlist. Whether or not you like that, is up to you. My own opinion : I like playlists, but not for the simple purpose of just listing an album.
In any case : these files are normally a few kilobytes at most. Deleting them, even in massive libraries, won’t free up any significant amount of space.