I'd like to back up the current (original) ROM of my phone before rooting so that in case I need to send it to repair, I'll flash it back.
The problem is: most back-up methods e.g. Titanium, Nandroid require Root. At the same time, one can only gain Root by flashing a ROM with Root. So, by the time one gets Root, the ROM is already changed. Then, how can I back-up my original ROM?
My device is Sony Xperia Z C6603 running Android 4.2.2 build number 10.31.A.0.244
I'm an Android developer so I'm completely comfortable with using