joining and filling two separate objects made with pen tool

I am creating a square and then on top of that I am creating a goofy looking roof/cap.

I used the pen tool only.

How do you join all the segments so when I fill the object it works nicely?

When you complete an object it appears from my frustration that you cannot select an anchor point on that object to start from and furthermore you cannot end a stroke on a completed object or it kills that anchor point.

Thanks for the help