Flash Cyanogen version from Omni version I have Sony Xperia L(C2104)(jellybean). Rooted my mobile, unlocked bootloader and flashed Kitkat 4.4 with unofficial random Omni Rom from internet, which obviously have some bugs(bluetooth, gps etc.). After this Omni version is installed I'm not able to work with any rooted applications(eg:titanium backup)[ROOT ACCESS DENIED]. So now I want to flash some stable cyanogen version OS of Kitkat. Do I need to root the mobile and follow the same flashing steps. Please suggest the steps to follow to flash cyanogen version kitkat in my xperia L which has omni version kitkat now. Let me know if in case need of some more info.
Do I need to root the mobile and follow the same flashing steps[?]


ROMs are not flashed from inside a running Android OS, and so root is not required now. All you need is flashable .zip file that can be flashed from a custom recovery, or a fastboot .zip which can flashed using fastboot. (You do have a custom recovery, don't you?)

Steps to flash the ROM:


Find the ROM of whichever version or name you want to flash, 
Download and copy the flashable .zip into the root of your internal SD card,
Boot into custom recovery, 
Wipe Data, System and all cache(s), 
Select Install zip and follow the instructions there. 


These are the most common instructions to flash a ROM. It is possible your choice of ROM requires certain additional steps, so do search on web. 

Make a Nandroid backup first using the custom recovery. Please don't ignore it, I can't stress more on this.

Disclaimer: Do it at your own risk!