Hi, this is my first time to scratchbuild a house. (Not my first attempt though! [;)])
I want to know what angle roofs are. 
That’s something like “how far is up?” They vary, but a peak angle of 120 degrees is pretty common. That angle is easy to lay out with basic carpentry and measuring tools. It is steep enough to shed water and snow in most cases; but it is not so steep that it becomes too difficult or dangerous for a workman to get up there and build it, shingle it, or repair it. It’s pretty easy to lay one out with a 30/60 degree triangle.
Tom
(edited due to rusty math skills!)
Thanks!!!
Charles
Here in northern Michigan steeper Is better due to snow loads. Nearly all building code roof angle minimums are based on maximum water depth possible on the roof.
I built a dozen houses from floor plans on the Antique Home Style site. Most of them have 120° roofs.
http://www.antiquehomestyle.com/plans/sears/1923sears/23sears-sherburne.htm
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
My Model Railroad
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Bakersfield, California
Most residential home construction have roofs measured as something like a 4:12 or 6:12 pitch for example. The rise per 12 feet is what it is expressed as. Your 120 degree roof angle would be 60 degrees to each side - that would be a 6:12 pitch. A lot of older western roofs and plot home have a 4:12 pitch. older bungalow style with the upper bedroom area are 9:12 or 12:12 pitch.
Jim
As Jim points out, roof slope is usually stated as a ratio of rise:run. He is wrong that it is for 12 feet, though. It TENDS to be in inches–that fits nicely on the size of a framing square. But, it is simply a rise for a given run. And that can be inches. Or yards. Or millimeters. Yup, metric!!! It is all the same.
Converting rise:run to angles is a simple exercise in trigonometry. You DID stay awake in that class, didn’t you?
Curiously, the obvious 1:1 ratio is rarely used. I assume it’s because it makes an ugly building. Well, awkward looking, anyway. Perhaps I am in error.
Ed
My first house had a 45 degree slope on the roof, referred to around here as a 12/12 pitch. This house was built about 1910, and had five foot side walls on the second floor eaves side.
A second consideration is that the roof was STEEP, and insulation space in the attic as limited. Maybe this contributed to the decline in this style.
Dave
Don’t forget houses with flat (actually nearly flat) roofs!
As others have mentioned, the geographic location of where your town is suppossed to be might help you answer your question.
Northern climates tend to have sharply pitched roofs in order for the weight of snow to sort of cause its own avalanche. That amount of snow might buckle a flatter roof. Older parts of town that mimicked the architecture of old Germany or Scandanavia, like you might find in Pennsylvania or Wisconsin, will have more houses with more sharp pitches.
Warmer climates can get away will shallower pitched roofs. Look at photos of modern Florida for example.
Not necessarily true, our house in Anchorage, Alaska had a relatively low pitched roof, but the structure was more heavily built than normal homes. The house near us with the high pitched roof actually had more trouble with the snow than our house had.
Twice, we had the roof shoveled off as the snow had accumulated over the winter to a depth of greater than 6’ of compated snow. The guy we had preferred doing our roof rather than the steeper pitched roofs.
Rick J
My favorite roof ever is a dead flat roof with a top membrane of stainless steel. Easy to frame, easy to clear, and lasts “forever”.
The one I know of is for a warehouse. I don’t recall where.
Ed