If you are having a home custom built you will also be choosing a new home roof in the process. If the home is in a housing development you may only be able to choose the color of the roof tiles.
If the development is in Southern California the new home roof will most likely be made of concrete tiles. If the home is in a high end housing development it may have a clay tile roof or perhaps a concrete tile roof made to look like the classic red Spanish tile roof both in color and shape.
And if it is a concrete tile it probably is a lighter weight tile than a real red tile roof component.
In developments in other areas of the country you may get a combination of different roofing materials on a new home roof, including asphalt shingles.
If you are having a custom home built for yourself then you can really choose just about any type of roofing material that is available. There is a custom built round house with a somewhat pitched round roof sitting up in the hills in Palm Springs, California that has a reflective copper roof and as you drive by with the sun hitting it just right the roof seems to glow. And metal roofs which include copper are a possibility for a new home.
The major downside to having a copper roof installed is the cost factor. However if you are spending the money in building a high quality custom home then choosing copper for the roof is always an option. Actually a copper roof is a good choice as it is does not corrode and can withstand extreme weather conditions and it also will last a life time.
The material is flexible and can be formed to cover just about any architectural style of home.
One thing about building a custom home is when choosing the new roof, in many communities there are building codes that may restrict your roofing material choice. Your architect will be able to tell you what you can do in these communities.