you need to make an air barrier between your roof and the beating sun, these hollow bricks are perfect for this job, old buildings like the ones in Lucknow use these.
Jumbolon is no use if you are trying to make it work in direct sunlight, A raised wooden structure covered with some skin is great too, just make some funnels to channel the blowing gale into that area, it will push out the heat from the structure. I have also tried an idea and I cannot prove technically how good it was but I used these same hollow bricks for walls in a standalone room on my house rooftop. I cut some channels on both top and bottom of the walls so air could move. I covered the bottom ones with mesh to keep insects etc out. I did feel at one time in summer that the top vents were slowly exhausting very hot air.
I cannot technically prove it but I think it helped keeping that room cool, the small "chooha" A/C I put there easily maintained 24*C. The room was 10x10x10 - btw it also had a sheet roof and false ceiling which I had lined with insulation foam.