Most regions of Spain, Mexico, Italy and the American Southwest have tons of heat and sunshine, and an abundance of Mission- or Spanish-style terra cotta roofs. Some ancient sites have clay and terra cotta tiles that have survived the test of time and relentless centuries baking in the sun. Basic clay roofing is light in color and doesn't retain as much heat as a darker roof. Modern clay tiles have paint treatments to make them look like more expensive slate or traditional terra cotta and to add weatherproofing and reflective capabilities.
Traditional rust or sienna-colored terra cotta tiles keep buildings cool through their shape as much as their composition. Terra cotta tiles go through a baking process in ovens, or kilns, which makes them harder and less porous in terms of holding lots of heat. Most often they're molded into a half-barrel or "S" shape, forming interlocking arches across a roof. Space beneath the arch of each tile allows for air and water circulation and runoff, which prevents heat capture and keeps the home below cooler.
Many clay and terra cotta roofs sit on top of concrete and stucco homes, and with good reason. These materials are heavy and need solid foundations for load bearing and wind and earthquake resistance. Another consideration with terra cotta roofing is that cold and wet weather often make tiles snap. Newer processes and treatments prevent this from happening, but checking for durability and temperature resistance is a good idea.