After I backed up my iPhone via iTunes to my computer, I restored the setting on my iPhone 5. My Camera Roll is empty.
The photos appear to be backed up on my MacBook, in my User's folder >Application support folder>MobileSync>Backup folder.
How do I get them back into my iPhone? (My music disappeared to, but I'll worry about that one later, as everything is on iTunes.)
Restore the backup that contains the photos.
For the future, copy photos from your camera roll to your computer. If you connect the phone to your computer it should appear as a digital camera to your operating system.