First thing is first. I did the same thing so I will help you if i can. The faces are all backwards. The front face is the white one. Im not sure what problems that would cause for you, but doing some more advanced things would be a problem. I came in here with a similar question and thats the first thing they told me. You might be able to reverse one then click orient faces on it, but sometimes that doesnt work and you have to do each one by hand.
As far as the roof goes, you can look here for a quick video on how to make a roof fairly easily. It is a bit advanced I guess you could say, but after some trial and error it shouldn't be too hard for you. After all you did get this far on your own right? Just make sure when you do it to select the face THEN select the follow me tool (the video will explain) then click the face.
When you triple click you will probably select the entire model, but dont worry about it.
Video: http://youtube.com/watch?v=A6WxE6oO3JU You may have to watch it a few times, but this video sure did help me out a lot.
Be sure to look at all the videos by that user, Aidan Chopra. They are supposed to go with his book, Google Sketchup for Dummies, but you can find them just the same without it. (Ive read the book btw, its very good)