How to make sloped roofs

To make sloped roofs like here: http://i46.tinypic.com/1t4lc8.png
You will have to do following:

• First make the area you want to make sloped from cubes like this: http://i48.tinypic.com/2zrf3gg.png
• Then select one row of the edges
• Hold down Q and point your mouse to the edge of the cube. (doesn´t matter which cube of the selected cubes)
• scroll your mousewheel forward (You still need to be holding Q)
• Do this for all of the rows and You have a nice roof :P