Make it metal
Unpainted metal roofs are naturally reflective (high solar reflectance), but they tend to hold heat in (low emissivity), so they are generally a better choice for steep roofs than for flat or low-sloping roofs, which receive more sunlight throughout the course of a day. A factory-applied cool roof coating can improve the heat releasing properties of a metal roof, enough so that some coated metal roofs are able to qualify as cool roofs.
A standard unpainted metal roof can be a cost-effective solution for some steep-sloped applications, since it is already reflective and requires no additional technologies or materials to achieve cool roof status. Factory-applied white paint increases the cost by about 20 cents per square foot over an unpainted metal roof, while the more efficient integrated cool-roof coatings can add $1 or more per square foot to the cost of the roof [source: Department of Energy].