TomLog over at BlenderArtists recently posted a really good video tutorial on how to make a Spanish style roof tile and then repeat the shape across an entire roof quickly and easily.
His simple approach to using Blender's powerful built in features really makes this tutorial great for Blender Beginners. Although probably geared for Beginners, as it uses rudimentary Blender tools, advanced users will probably find that using a single tile and then using two array modifiers would allow for a much quicker and easier to tune tile roof (see example below). Regardless, his approach is effective and it works.
Below you will find links to the Video Tutorial and accompanying .blend file. If you would like to read the original post head over to Blender Artists!