Found this site (among many others) that gives different roof styles:

It is handy for adding variety to town maps.

Also, there is another style I have seen on some of the farmhouses around here, kind of a modified hip roof:
Click image for larger version. 

Name:	2008-03-14_092752.png 
Views:	1278 
Size:	2.5 KB 
ID:	2757

-Rob A>