Unhappy Help me install kernel by DoomLord

i have unlocked bootloader & rooted device in .254
then i upgrade it to .266
when i want flash your kernel >> http://forum.xda-developers.com/show...php?p=50272149

it say:
15/015/2014 09:15:42 - INFO - <- This level is successfully initialized
15/015/2014 09:15:42 - INFO - Flashtool Version 0.9.11.0 built on 2013-06-04 22:50:00
15/015/2014 09:15:47 - INFO - Device connected in fastboot mode
15/015/2014 09:15:55 - INFO - Selected kernel (boot.img or kernel.sin): C:\Flashtool\firmwares\SP_DooMLoRD_AdvStkKernel_FW-266_v01.elf
15/015/2014 09:15:55 - INFO - Flashing selected kernel
15/015/2014 09:15:55 - INFO - sending 'boot' (11009 KB)...
15/015/2014 09:15:55 - INFO - FAILED (remote: The Device must be rooted first)
15/015/2014 09:15:55 - INFO - finished. total time: 0.008s
15/015/2014 09:15:55 - INFO - FASTBOOT Output:
sending 'boot' (11009 KB)...
FAILED (remote: The Device must be rooted first)
finished. total time: 0.008s

15/015/2014 09:15:55 - INFO - Please check the log before rebooting into system

Why the device have to rooted first? Or i have to unlock bootloader again?