Is the technology of photos remaining in albums and deleted from the main camera roll super difficult? I’m not a tech expert, but this seems like there should be an easy way to enable this in an iPhone.
That's seemingly just not compatible with the way Apple chose to implement Albums. Albums are not storage locations; they are just lists of photos that exist elsewhere in the library.
The Photos library on my iPhone has a "Library" section broken into views by date captured: Years, Months, Days, and All Photos; the last should show everything in my library (except hidden photos), while the first three show abbreviated summaries by time periods. I also have a Recents view (Album) that also shows the entire contents of my library but shown by date added to the library (which could be different for imported photos). Do you have something labeled "camera roll" in your copy of Photos?
Apple has changed it intentionally to be this way, when Photos came out. In Apple's previous photo apps (iPhoto or Aperture) we could modify the basic storage structure of the library and move photos between events (in iPhoto) or projects (in Aperture). In Photos this is now done automatically - Photos is creating the Days, Months, Years for us. This ensures, that the basic structure will be the same on all our devices using iCloud Photos.
But albums have always been built on top of the basic library structure, and the albums have always been referencing the photos in the library, so we could add photos to many albums without having to duplicate the photo. This has not been possible in the events or projects - if we needed a photo in more than one event we had to duplicate it.
Photos in albums can be deleted from main library
