What is Camera Roll

The camera roll is a place in the Photos app where all your photos and videos are saved.

On a device without a camera the camera roll album is called "saved images", because other applications can add images to it, but it is holding all images in your Photos library as well. When you create albums, the photos in the album are references to the one copy in your camera roll. The photos are not duplicated, but just references to the items in the camera roll. You can add a photo to many albums without needing more storage.

Is this in the Photos app? More information would help.