|No, not utterly hip roofs, cool roofs.|
Cool roofs are exactly that, temperately cool roofs that lower the overall heat within a building by both reflecting solar rays and quickly re-emitting those absorbed. Cool roofs are far from being a recent innovation, and their principles are seen in the simplest of understandings, in the way people wear lighter colors on hot, sunny days and how PE uniforms should typically be a light gray. In many countries, residencies are painted entirely white to take full advantage of this idea, most notably in Greece's coastal regions like Santorini.
Cool roofs should be implemented whenever necessary, and with Southern California's constantly increasing temperatures, year after year, a large part of green architecture has become how to effectively design a roof that benefits the building as well as the public inside.
Cool roofs are both conscious of their own environment as well as the landscape around them. Within any mass of construction, there exists a level of heat which the buildings emit back into the air. Take a typical residential street block and a graph could be made of how much heat each house emits. If one particular house is producing a larger amount of heat, this affects the neighbors beside. Now imagine this idea but within large, metropolitan areas, greater multiplying the effect. If one building is producing a much greater amount of heat, then above it is what many call a "heat island". This dramatic rise in heat can also produce a greater amount of smog directly above the building.
The most appealing part of all? It's very easy to do. Cool roofs can be an afterthought, though they never should if appropriately designed, and can still have a great impact. All that is essentially required for minimal effectiveness is to coat a roof in a light color, or better, to use a material that is both light in color and low in heat absorption.