Hi Fore,
When you check your two directories in Storage Locations and then click back to Album view, you’ll notice that the two locations appear as Focus search filters at the top of the screen. Clicking on the + icon in a Focus search filter will invert it to - and show all albums which don’t satisfy that filter.
When you add your husband’s library in another location, you’ll be able to Focus on your library or his using the location filters.
Once you have a Focus you can create a Bookmark for it and recall that search with a click. Focus searches are dynamic and will apply the filters to the whole library as it changes.
You could enable and disable different watched folders for each library, but it might restart import or analysis of the library each time. It’s also a bit more work to get Roon into the right state for each of you, whereas the Bookmark method let’s either of you see what you want with a single click.