Pretty much every roofing product is water resistant to some extent. Obviously, some materials can withstand far more moisture than others. Homeowners who live in moist climates and are considering roof replacement need to make water resistance one of their chief criteria when choosing a product. Of course, while many products can withstand moisture, they could have a shortened lifespan and require more maintenance over the years in climates where it is particularly wet.
In the wettest and rainiest climates, you generally want a product with some sort of glaze, paint, finish, or waterproof texture. For example, terra-cotta tiles are extremely popular. But, most terra-cotta products have no powder glaze on the tiles. Terra-cotta itself is relatively water resistant, but it will absorb some of the moisture. This usually doesn't actually damage the tile, but it does eventually lead to the formation of moss and possibly mold on the surface. Also, when a raw terra-cotta tile gets wet, it becomes darker, which some people don't like.
All of this is also true with concrete, clay, stone, and many ceramic tile products. But, all of these materials can also be found with glazed or painted finishes. A clear glaze on a terra-cotta tile will not change the color of the roof, but it will make the surface waterproof. Similarly, a painted concrete tile will deflect water, rather than absorb it. You really can't go wrong if you buy a product that has some sort of waterproof finished that will protect the surface from moisture. Smoother surfaces also help water to flow down them more quickly. So, roof leaks are going to be less common.
Avoid Wood Roofs
It is also good idea to avoid real wood shingles or shakes altogether. Wood is one of the most liked roofing products because of the way that it looks. But, it definitely isn't smart in a clmiamte where it gets rained on every day. Even though you might notice than many of your neighbors have wood roofing, it just won't last as long or offer as much protection as other finished materials. There are composite wood products that are fully waterproof and longer lasting then real wood. Do these look like real wood? Not exactly, but it is hard to tell the difference on a tall roof that can only be seen from the ground (over 10' away). Any way you look at it, they are definitely a better choice if you live somewhere rainy.