@lilleskut said:

I just started playing around with sketchup and made a house with a gabled roof like here: http://www.et.byu.edu/groups/cmfac/fenn/CM210/notes/Roof%20Systems/roof%20types.jpg.
What I want to achieve now is the following:

make the roof to extend beyond the walls on all sides (overhanging) add equally spaced columns at the end of the roof on all four sides of the house. The columns should extend from the ground to the roof and connect to it smoothly.
How do I do this? Another, general question I have is: "How do you create a set of objects equally spaced?" Is there a tutorial explaining this?

Check this out.
Aidan Chopra has a complete set of tuts on YouTube... everything you asked and more!
http://www.youtube.com/results?search_query=sketchup&search=Search