FAQ: How do I delete something from my library?
You can delete anything from your library by selecting it, then pressing Delete on the selection menu.
Please keep in mind that this is a destructive delete, and the selected tracks will be removed from your hard drive. Deleted tracks are not available in the macOS Trash or Windows Recycle Bin after they are deleted.
There is also the option to Hide tracks and albums, which doesn't touch the files on your hard drive, but instead just hides the files from Roon.