Energy efficiency of roofing materials
The coolest roofing is painted white metal roofing. If white doesn't fit your aesthetics, there are special "cool color" coatings that have a medium or dark color with the solar reflectance of a light color. They reflect infrared wavelengths. There are a few shingle roofings that have that have the cool color technology, but smooth cool color metal is still more effective. The easiest gauge is to select an Energy Star labeled roofing. Best is high solar reflectance rating, and high emissivity (to cool off at night).