On iOS devices removing photo from album does not remove it from camera roll, and it’s inconvienent to switch to camera roll to find and delete the photo, soon there will be unwanted photos not in any album still taking up place, on iPhoto Mac these photos can be found by creating a smart album, but no obvious way to do this on iOS devices, any ideas?
The best solution is to use the system as the developers intended, despite the inconvenience.
For Albums created on the iOS device using the Photos app (I believe the same applies for Events created in iPhoto on iOS):
Deleting a picture from an album removes it only from the album.
Deleting a picture from the Camera Roll deletes the photo from the device—but it may still be part of your Photo Stream.
Deleting a photo from Photo Stream removes it from the stream, but will not remove the photo from devices on which it has been included in Albums or Events. ᔥApple — iCloud: How to delete photos from your Photo Stream
There is no magic incantation that will reveal photos you’ve deleted from albums.