How do I back up a photo album on my iPhone that was synced during phone upgrade?

I have an iPhone 5s. There is a photo album on the phone that came from my old iPhone when I upgraded to the 5s. I just upgraded to iOS 8 and I would like to use iCloud Photo Library. I went to turn it on and I got a message saying that photos synced via iTunes will be removed and it tells me how many photos. It is the exact number of photos in this album that came from my old iPhone. I do not want to lose those photos.

I made a backup on my new computer in iTunes but then I also read that iTunes doesn't back up photos that aren't in the camera roll.

So, I need help figuring out if it's true that that old album on my phone did not get backed up, and if not, then how do I back it up? I really want to use iCloud Photo Library but I don't want to lose this album of photos.

Thanks for the help!