Need help troubleshooting topic

Hey guys i was hoping someone out there can help me out. My phone just got the message to update to 5.0.1, but when i tried to update it, it would reboot then load to around 40% of the update then say error with a little android on his back with a red triangle on his stomach. So i thought this was because of my phone being rooted and unlocked, so i unrooted it and locked it using Nexus Root kit, and when i tried to update the phone to 5.0.1 it still gives me that error message. Some things to note my phone was ATT and i did delete the ATT bootloader immage and all of there ringtones when my phone was rooted. Please help