If the Rom was rooted before,relocking the bootloader should not have had an impact,unless you had to run an ruu to get the phone to boot.
If superusr is still in your app drawer,then try entering "su" after "adb shell" if you aren't allready. You'll need to be at a "#" prompt.
If you ruu'ed and are 100% stock now you'll have to:
-reunlock
-"fastboot boot" recovery. Don't actually install it with "fastboot flash"
-use fastboot booted recovery to install supersu
-relock
The phone should have no issue booting if superuser is the only mod. Boot,recovery are 100% stock,and system is 99.9% stock
Did you do an unlocked dd of mmcblk0p7 as well? If not,do one after installing superuser,but prior to relocking. Do another after the relock
Thanks! Holler if you have more questions