I found easyrafters.com has a free 30 trial download for their software. Its super easy to use. You just pick what kind of roof, how wide the roof is supposed to be, overhang, slope..... and then you can print out your plans for rafters for your project. 30 days is plenty to print several sizes and kinds of roofs for future projects. It even works on mini coops that only have a 3ft roof span.