Your camera roll photos and videos are only contained in your backup, and can only be accessed by restoring the backup to an iOS device. Photo stream photos are the only ones synced with your iCloud account.
If the photos and videos are on your phone now, import them to your computer as discussed here: http://support.apple.com/kb/HT4083. If they are only in your backup, you'll have to restore the backup to your phone to recover them and then import them to your computer.