This is a roof we built and tiled with concrete tile a few years back. I matched another cone that was on the front of the house If you can build them, you have to know how to roof them.
http://picasaweb.google.com/crookston.john4/ConeRoofing?authkey=Gv1sRgCMm95rjVxpn7Fw#5357751460506866226>>>
I am working on a church like that right now. The tiles are Ludowici French and they are made just for the cone you are working on. This church was built in 1914 so it is about 100 years old; and the different rows are numbered; 1-2-3-4-....on their backs. They go right on around the cone. I wrote an article in Traditional Roofing magazine last year showing you how to do that with any roofing material. I believe if you write "conical roofing" on Google it will come up. It works for slate or tile or whatever.
The tile on the picture I posted are Vandey Hey Raliegh turret tile. We laid them staggered too. They lay up like wood shingles and they have a 2 inch headlap. All of the tiles are solid and there are about 5 different shapes with different angles cut in. You just have to mix and match. We have done dozens of them over the years. Very nice looking!>>>
Those tile look like they don't have built-in sidelaps like the field tile. Looks like a challenge.
This is a picture of a place in SLC that I did a repair on in the '70's. It's clay and I was amazed at how every course on the cone was a different size and was installed without needing any cutting.
http://s647.photobucket.com/albums/uu195/GWMiller/Roofing/?action=view¤t=McCune.jpg>>>