Clay tiles are one of the oldest roofing materials still in use, and it is, in fact, one of the most common ones around the world. Part of the reason for that is the durability and cost compared to other materials. A clay tile roof can also be very beautiful.
Weather conditions that will damage other roofing materials, such as heavy rain, hail and wind, are no problem with a clay roof, and fire does not pose a hazard.
You will also save money on your heating and cooling bills since it has a high thermal capacity, meaning that it will prevent temperature fluctuations in your home.
Installation of a clay tile roof might end up costing you more than other materials, since it is heavier, and thus might require reinforcement of you roof. The tiles are also brittle, so unless they are handled correctly, they could break during installation. However, once the roof is installed, it will last you a very long time.