Obstruction & Denial Of Easy Access of the Terrace.

My query is that the second floor owners have roof / terrace rights without any exclusive rights & ownership rights of the roof. The utilities of all the floor owners GF /FF / SF (water tanks / dish antenna / outdoor units of AC etc) are located on the terrace with each floor owner having joint rights to maintain their respective utilities located on the terrace of the building. However, the entrance of the terrace is locked by the second floor owners & have kept the keys under their custody. Several times they have kept the roof locked even when they are out of town for few days/ weeks. Many a times we have demanded separate keys for easy access to the terrace which they have denied. My questions/ concerns are as follows : 1. Can the terrace of any such building be locked by a person having roof rights ? 2. Even if it is locked, shouldn't the other floor owners have separate keys for easy access & maintenance of their respective utilities? 3.Should the other floor owners not have the keys to maintain their respective utilities & to avoid any mishap? 4. Why should the other floor owners be dependent on the floor owner with roof rights, every time they have to execute & maintain any work related to their own utilities? Request you to share your views and clarify a remedy in light with the existing provisions of the governing statutes. It will also be helpful if you can let me know which Act or Rules or Authority will be the most appropriate to be referred/ approached. Thanking in anticipation.