Yes of course jee mains is a national level examination. In whatever state you belong you can apply for csab and the special rounds as long as your nationality is Indian. So if you have not got any seat in the 8 rounds or want a better college go for csab counseling 

dear candidate,

yes you can apply CSAB in the institutes which fall under SFTI ( self financing technical institutions). CSAB SFTI (Self Financed Technical Institutes) 2019 will offer admission to candidates with valid JEE Main 2019 scores. The seats will allotted to registered candidates on the basis of their merit in JEE Main exam, choice filling and seats availability.

hope it helped.