Clay tiles also known as Spanish style roofs, go all the way back to 10,000 BC. They are durable and require little maintenance after they are installed. But being organic in nature does make them prone to moss. This moss does require cleaning or it will cause moisture damage to the tile roof.
You can clean your Spanish style tiles after a few warm dry days. The moss can not cling under these conditions, and this makes it easier to remove. Sometimes under these conditions you can pull the moss off the tile with your hands.
Always practice safety first, especially on Spanish roof tiles. Have a sturdy ladder and shoes with good treads. Always wear gloves, don't touch the moss with bare hands. And you may want a mask for the dust.
Make sure when you set your ladder against the house it is on level ground. After getting up to the area where the moss is, you can brush the moss away with a wire brush. Always work from the bottom up, this will help you keep your footing. The moss should just flake away.
You can then remove the loose moss with a stiff broom. Sweep it off onto the ground. Repeat the process until all the moss is gone.