I think you posted this in another thread, and I said the same thing there: If you want us to help, you need to give us some information to work with. What ROMs did you flash? What method did you use to root? What recovery (TWRP, CWM?) are you using?
Without that information, we can only guess. My guess is that you flashed a ROM meant for a different version of the S3. ROMs are specific to the exact model and carrier, so if you flashed a ROM meant for (as just one example) the international version to a Sprint phone, then you've almost certainly bricked your phone. Search on the word JTAG, because sending your phone off to a service that can flash the correct ROM via a JTAG device is the only way to repair a hard-bricked phone.
Next time, READ, READ and READ some more to make sure you know what you're doing.
EDIT: I now see you didn't post in another thread, you posted the same request, and got the same answer, in this same thread. If you don't know what you did, you're completely out of luck. Non of us can magically figure out what you did to your phone, or examine it remotely. What do you expect us to do without any information at all?
I told you to search on JTAG:
Let me google that for you
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