Now for the beveling of the 3 pieces you have put together. I make a duplicate of each one, I did it one at a time, you can do it however you want.

Once I have made my duplicate, I then drag the new duplicate down to the orignal piece, in the righthand stack.

Then go back the the work area and line them up together, one on top of the other. You want to select the bottom layer, and go to TOUCHUP/BRIGHTNESS & CONTRAST and use the BRIGHTNESS bar to make this piece darker.

Once you have that layer dark, you will click OK and go back and select the top layer, and go to EFFECTS/EDGES/SOFT EDGES

You drag the bar to the right, you can make it as wide as you want.

When have done these steps, your roof should look like this

Once I have done this, I lock the 2 pieces together. And you will go on to do the other pieces of your house, except for the back side of the roof, I didn't bevel that. Here is my beveled house