I agree that there is more than one equally valid preference for what should get higher priority in results. This may differ between persons but even the same person will have different preferences depending on current scenario. Sometimes I may want to find things I don’t know, sometimes things I know / have in my library.
Arguably the Roon search would need preference settings for that. I think the way it works now is that it tries to find some medium, and if you only want library results you are expected to click the library button.
If I know that something is in my library, I typically use the filter options and not the search.
There is a long-running search thread where you could add your feedback. I think Roon monitors this even if they don’t respond to everything