The angle of incident Sun rays changes throughout the day from East to West with the azimuth of the Sun. More to the point for this idea, however, the altitude/zenith of the Sun rays changes angles between seasons. One could take advantage of this seasonal variability by constructing a specially angled roof shingle or panel to preferentially cool or heat when needed the most. (See here to find the Sun's altitude on different dates.)
image credit: http://www.mpoweruk.com/solar_power.htm
In the summer, the sun has a higher elevation in the sky, and you would face a light-colored, highly reflective surface perpendicular to the rays to ward off heat. In the winter, the sun has a lower elevation. A different portion of the same roof panel would present a dark-colored, highly absorptive surface to the incident rays to capture heat.
Each installation would require shingles with orientation labels (e.g. "Face this edge South") and a calibration process to optimize for roof pitch and geographic latitude.
IDEATION: November 2010