HOW MUCH android OS TAKE MEMORY IN DEVICES I need answer that how much memory would take any android os on devices. 

can i root device and install kitkat os which device have already gingerbread .
There's no one answer to this question: each device has its own build of Android, so Android takes a different amount of storage on different devices. Whether you can install KitKat on your device depends only on whether there is a KitKat ROM for it. See When will my device get the Android 4.4 update (KitKat)? and Where can I find stock or custom ROMs for my Android device?

Rooting the device is completely unrelated. You don't need to root the device to install a new ROM, but to install an unofficial ROM you will need to unlock the bootloader. Usually you do this with the fastboot utility, but details are different for different phones. See bootloader-lock to learn more about bootloader unlocking.