You can “delete” a Tidal album from the Roon library by un-favoriting the album within Tidal. All you have to do is a simple right mouse click. That is a faster method than anything within Roon.
I think Roon and its users struggle with this because Roon is not a media file management product per se - you cannot move or copy media files (except as part of the library importation process) and you cannot edit file embedded metadata. But yet the one FILE level function Roon provides is delete. That’s a little bit like a store that says we won’t carry weapons like guns or knives because they are too dangerous but we sell nukes.
Plus, the duality of “delete” meaning “delete from hard drive” for local libraries and “un-favorite” for Tidal albums is probably confusing to some users, and this probably generates some of the unintended local deletions. The menu choice is the same, the results are drastically different.
Point being, if Roon is going to avoid being in the business of FILE level library management, get out of that business entirely. It confuses users to have one function and not the rest, especially since that one function means two entirely separate results depending on context. Plus there are perfectly good tools outside of Roon to accomplish this. Just get rid of delete, let that happen outside of Roon. Then with Tidal albums, there can be a “remove from Tidal favorites” or “unlink from Roon library” type of command that is more clear. I suppose there would be an analog within the library to remove a file or album from the library without deleting it from the HDD, but that I think is the same as ignore or hide, really.