Hmmm, in that case, here's what you need to do:
Take some construction paper (or a brown paper bag) and cut out strips twice as thick as you want your exposed shingles to be long.
In other words... if you want 3/16" shingles, then cut your strips 3/8" wide.
Then, use scissors or a knife and cut tabs into the strips half way across. You should end up with like a "comb".
Using a glue stick (cheap at Wal-mart or Office Depot - look like lipstick) and start at the base of the roof, glue your strip. Start the next strip 3/16" higher, so that it covers half of the strip below it. It helps to draw lines on your roof every 3/16" before you start. Make sure you stagger your strips so that you get the neat "brick" pattern. It's ok if it overhangs the edges... just cut the excess off when you are completely done. Then, take another strip that DOESNT have tabs cut into it, and fold it down the center... use this to cap the roof top.
It will be something like this:
http://www.the-gauge.com/forums/showthread.php?s=&threadid=7295
(3/16" is just an arbitrary size I chose... you would use whatever is appropriate to your building.)
Hope this helps!