Managing iCloud storage

[Notfootball]

I have an iPhone 5 and an iPad and I keep getting messages saying that I don't have enough storage for a backup. I can see in 'manage storage' that it is my iPhone camera roll that occupies most of next backup and here's where a iPhone idiot gets confused. My camera roll goes back to last Christmas so I assume that all of this has been on the photo stream and therefore backed up to my iCloud already, is this right? If this is the case, I should be able to delete all photos on my camera roll as they are already on mly iCloud, right? If all this is correct, why would the phone need to backup everything on my camera roll since it is on the iCloud already (next backup size = 4.3 gb, camera roll =4.1 kb)?

I would really appreciate if you could answer in layman's terms as I don't get this at all!

TIA

[xalyssx]

Double check your icloud before doing anything. Iphones do try to back up everything all the time.

[Notfootball]

Thanks xalyssx.