I think your phone is closest to the model for the AT&T phone so I'll move the thread to that All Things Root forum
You said you made a backup before flashing the rom? Yes, you could just restore your backup to go back to where you were. If your backup was rooted then you will still be rooted. If you want to go back to complete stock, do this:
First check this thread
and download the stock rom for your phone. Or go to Sammobile Firmwares
, type the model number for your phone in the search and download from there. I think both are the same download link. You will need to use Odin to install it.
If you haven't used Odin before look at this guide
. Just DO NOT
use the stock rom files in that thread. Use the one you downloaded for your phone. Getting into download mode may be different for your phone too. Probably Volume Down + Home + Power.