There is research that shows that white coloured roofing causes increased heating elsewhere, so it's not a fix-all solution.

I live in Australia and during summer use a lawn sprinkler on the roof. Using a tap timer, it runs for 10 to 30 seconds every 10 minutes.

Just enough to wet the roof, so that the water evaporates and cools it down.

Other things you can do is growing creeper vines over a wall where the sun hits in the afternoon to keep direct sunlight off the wall.

If you have sash windows, you can open it at the top and bottom, creating a thermal airflow that will cool the house.

Adding sunshades and building housing with awnings makes a massive difference.

Lots of research associated with passive solar temperature regulation.