Is the iPhone jailbroken? If so, it could be a folder permissions issue. You should be able to rectify it by SSHing into your iPhone and and navigating to the mobile media folder and changing it's permissions to mobile user.
You also may need to reboot in order for the change to take effect. I believe the folder is under /private/var/mobile/Media, where you'll want to change the DCIM folder permissions. If you're using WinSCP for your SSH access, you'll also want to select 'Set group, owner and permissions recursively' before pressing OK to make sure it effects all subsequent folders and files.
After a reboot, you should be seeing your pictures show up in the camera roll.
Let me know if that helps at all