Toyota (the car company) has developed a turf roof "tile"

Found this on a website.http://www.worldchanging.com/archives/004890.html
 Japanese website is here http://www.toyota-roofgarden.co.jp/ryokuka%20jigyou.html
The guys who sell the tiles are here http://ryokuka.yamazaki-sangyo.co.jp/

Might be an idea for some of the roof of the house (the flat section in the southwest corner as per the concept)