I have simple bitumen roll roof with additional insulation, no air pocket space, no nothing and heats up a lot in summer.

I have been considering either heat reflective paint or installing solar panels. My research so far, suggests that reflective paint may not adhere properly or peel off in few years, while the solar panels get heated themselves and it's unclear if they would be of any help or actually worsen the situation, even with air space between them and the roof. With no prior experience, I am lost.

What are the most efficient methods for heat protection (not confined to the above mentioned ones), disregarding cost and installation complexity for the time being?