Well it doesn't matter to which state do you belong for the JOSAA and the CSAB counselling. I think you are getting confused with the CSAB-NEUT counselling which is conducted especially for the north eastern state institutes.

Once JOSAA counselling is finished, only then the main CSAB counselling will begin to conduct the special rounds for admission in NITs/IIITs and GFTIs.

CSAB-NEUT does not give admission to NITs/IIITs so keep this in mind.