Attached Link: http://sketchup.com/eval/

Go to the site above and download the demo of Sketchup. It`s the full thing and you get to play with it for 8 hours working time. It`ll take you about 2 minutes to make a roof like that and then you can save it as 3ds. No modelling experience needed. It`s a piece of cake. Before you do anything go look at the tutorials on the site. They play in media player and are an example of what a tutorial should be. The only downside is, when your eight hours are up, you`ll want the prog and it`s $500. Let me know what you think if you try it. Good luck.