When you sync photos in iTunes, that takes photos that you have selected on the computer and syncs them to the iPhone. Photos in the Camera roll are not synced in iTunes, they are, however, saved in the backup. If you restore the phone to a backup that contained the photos, they will be brought back. If you have pictures selected in iTunes from the computer set to sync and sync, then they will be synced to the iPhone. This is all based on a couple of settings. Importing the photos from the camera roll is only accomplished by specific software on the computer. While this can differ between computer OS platforms, it is generally the same. Photos will not come back to the Camera Roll with a sync, only from a backup.
iTunes does not save all of this in a sync, is saves content on the phone in the backup. It will not re-upload things that you delete unless you restore a backup that was made before items were deleted. Actually, you cannot delete photos that have been synced to the phone, on the phone. Those can only be deleted by another sync. If you have a general checkmark by your photos folder to sync, and when you import photos to that folder from the camera roll, they actually would sync back to the phone during a sync and it would seem that it is syncing back content that you deleted, but that is all based on your settings.
