Is there anyway to backup current ROM without unlocking bootloader/ installing clockworkmod recovery? I'm trying to use ROM Manager app to backup the current ROM of my Xperia Z but it seems that cannot be done without unlocking the bootloader/ installing ClockWorkMod Recovery.

Is there any alternative for me to backup current ROM and flash another ROM without having to mess with bootloader or ClockWordMod Recovery?

Note that my device is already rooted using this method.  

According to Sony's website, messing with the bootloader is likely to void warranty which defeats my purpose and so all my attempts to backup the stock ROM here.
I found another way to do it. This one uses Terminal Emulator or adb shell.
Open a shell as root. You first determine what device blocks /system and /boot are, with ls -al /dev/block/platform/dw_mmc/by-name. Note that the dw_mmc may vary between devices. You'll need to find it yourself. Then dd if=/dev/block/systemblock of=/storage/sdcard0/system.img and dd if=/dev/block/bootblock of=/storage/sdcard0/boot.img will backup all your Android system. 

If you want to restore using this solution: boot into recovery, mount your SD Card, then in a adb shell, do 

su
dd if=/storage/sdcard0/system.img of=/dev/block/systemblock
dd if=/storage/sdcard0/boot.img of=/dev/block/bootblock