Thats strange, as I've just been doing exactly this on my new 7. I have a few important photos on my iPhone5 with I didn't want to risk loosing through a back up restore to my 7, so I emailed them to myself from my 5 and opened the emails on my 7, held my finger on the image until a box popped up with options on what to do with the photo, I just tapped on Save Image as below and they go straight to my Photo roll...