I have met the same problem before. Then I found software that capable to transfer all your iPhone camera roll to computer. Therefore, you can free enough space on iPhone to store the important data. Also, you can back up your camera roll routinely in case of accidentally deletion or lost. This mighty and useful tool is iOS Transfer.
iOS Transfer is a photo manager for iOS devices. You can check the following guide to learn how to move your camera roll from iPhone to computer.
Click the download button below to download this tool base on the operation system. Read the guide below to see how you can achieve it.
To begin with the process, you need to download and install iOS Transfer on your PC. After that, connect your iPhone to PC with USB cable. The device should be detected in seconds.
Step 2 Copy iPhone camera roll to PC
Check the "Photos" - "Camera Roll". You'll see all of your iPhone camera roll photos at the manager windows. Select the ones you want to transfer, click Export to – Export to my computer. You will get it done in less than a minute.
By this means, you can easily transfer iPhone camera roll to your computer. If you are using a Mac, you should follow the guide how to transfer photos from iPhone to Mac.