flat roof on circular earthbag home

I plan on building a 24 foot diameter home, i am having trouble figuing out, the simplest way to put a flat slightly sloped roof on it. I dont want reciprical roofinf, and i dont like the idea of custom measuring and cutting thousands of slats for my roof. I would rather just use sheets of pluwood, without having to measure and custom cut every piece. Any ideas or links to how it can be done?

http://www.themudhome.com/earthbag-building.html

This link is to a ladies house in turkey. She has a flat roof on a circular house. I cant remember how much detail she goes into but her houses is on a few other websites so you may be able to piece together the details.

Earthbagbuilding.com has tons of info also