As a Top Floor Owner with roof rights am i eligible to lock terrace

Hello , I own a top floor flat(3 floor building) in ghaziabad for which i paid extra amount to require roof rights when i purchased it from builders directly. Recently i have decided to lock the terrace for security purpose also i actually find some things(drink bottles etc) which indicates that some people have been visiting our terrace without our permission(i am sure one of them is a family that lives in first floor). I am willing to provide access to other flat owners (first and ground floor) in case of any requirement which is specified in agreement like maintenance of water tank/antenna etc but first floor owner asking us to provide him with a separate key for the terrace . I would like to know if i can lock my terrace without providing a separate key to other flat owners as per law. Ground floor owner is totally agree with us and not demanding for separate key. Please let me know if i need to provide any more details to make my situation more clear. Any help is appreciated