Carpentry and Woodworking - Angle question for shelf top (roof)

Here it goes...I want to build a shelving system that resembles a dollhouse for my young daughter. It will be approx 4 ft long, 4 ft high (maybe a little longer). Three shelves with various dividers spaced in diff places for each shelf. The top of the shelve will resemble a roof. I'm assuming I pick a pitch for the roof and cut my angle for the two roof peices accordingly.

My question is - Do I use the same angle for the side peices, so they cleanly intersect (support) the roof? If not, how do I calculate the angle for the sides? Hope this makes sense, and I don't catch too much grief for the project.... :).

For any given angle for the apex of the angle, the angle for each end of the shelf will be one-half of the difference between the apex and 180 degrees. For instance, an apex of 60 degrees will mean each end is cut 60 degrees ( 180 - 60 = 120, 120/2 = 60) The sum of the angles of a triangle is 180 degrees.

Hope this helps.

With a 45 degree roof, the two side wall that intersect the roof will each be mitered at 45 degrees. The apex of the roof can either be a butt joint, i.e. both 90 degrees, or you can miter them at 45 each.

I nearly built one myself. But I stewed over weather or not to use biscuits on the wall/roof joints.

Thanks guys. I plan on mitering the roof joint. For support, I plan on some kind of face and a few triangle (don't know the tecnical term) blocks under the roof joint.