Dear labeeb 

As per the policy of JEE, only the candidate with OBC,SC,ST reservation can apply admission under reservation.  There are no other reservation like PWD or Ex Serviceman is allowed.  In case of Jammu and Kashmir candidates,  RBA category is counted under OBC category only. So you just need to ask your district council to give you a obc certificate stating you in RBA category.  No separate need of RBA certificate.  Also contact the JEE administration for further details. I hope it helped