How can I delete photos from camera roll and leave in an album?

I created a named album on my iPhone and placed photos from my camera roll in there. I would then like to delete these photos from the camera roll. However, when I try to do so an error messages warns that the photos (which currently reside in the the camera roll and named album) will also be deleted from the album.

Is there a way to delete the photos from the camera roll and leave them in the specific album?

You can't. iOS uses a simple photo database, very similar to iPhoto. Primary storage for all photo image data and metadata (time, place, exposure, etc) is the camera roll. This system lets you create the illusion of multiple albums, and storing photos in the albums.

But from a database perspective, your album is just a table with the image ID of every photo you place in it, creating a link back to the image data in the camera roll.

You can delete photos from albums, thereby removing them from the table.

When you delete a photo from the camera roll, you delete the photo from the system.