Listen very closely.
Well, first of all I'm shocked that you bricked it on a root but anyway....
This is an easy fix do not worry.
Download "Odin" do q Google search for it you'll find it.
Then do a Google search for something like "galaxy's s3 mini stock sbf ROM" what you are looking for is a .sbf file of the stock ROM on your phone. You will find one somewhere. I will get on my computer I'm a little and I can find some links to this stuff
Download the Samsung kies drivers.
Then, enter download mode on your phone (again Google search will tell you how it is a key combination) plug it into the computer via USB.
Then fire up Odin. Click on the PDA icon. Select the. tar file you downloaded earlier (likley in your download folder) and click start on Odin and after 10 min your phone will have a factory image. Some of your data will stay some won't. The SD card isn't touched. Hope you backed your internal storage up although it usually doesn't mess with it.
Link to odin:
Download Odin 1.85
This is a link to the download file. It is actually in .tar format. not SBF. This is ok. do what the instructions say in this lik and you'll be good.
This also tells you how to put it into download mode.
Root for the Galaxy S III Mini I8190
You will have questions I'm sure so ask them here and I will answer or someone will. .
Sent from my DROID RAZR using Android Central Forums