How to construct roof top swimming pool?

You think that can be answered in a simple thread?

Actually the answer that CAN fit in this thread is hire a licensed and experienced pool contractor with that sort of experience that knows what all needs done and to find out IF it can even be done.

With a qualified structural engineer. Remember, a 1000 gallon pool, quite small, has 4 TONS of water

Before you spend money, check with local building department to see if it is legal.

Chuck

I doubt that your house was built to take the weight. The fact that you are asking without any mention of your structure is not a good sign.