We would need to know what is your style? Color and fabric preferences? What will the second bedroom be used for? Pictures of what you already have (and want to keep) would be most helpful, as well as pictures of the flat.

Hello aju007, Be certain that the structure is sound prior to placing anything on the roof. After that has been determined, you might think about using it for either a deck with cozy chairs and table or a garden area. A few Houzz examples: Best of luck and please let us know if we can be of additional assistance, Elizabeth Cabell, ASID, CID Cabell Design Studio

We could really use a floor plan to help visualize what you have.

Natural Stone finish tiles are better for the above description . https://www.somanyceramics.com/floor-tiles-durastone/ Thanks, Amit Cornerstone Designs Bangalore