Because I'm in FL, and have no snow loads, I can cheat. I used 2x6s for the ridge pole, and the top on which they rest. 2x4s for the rafters. Rafters are set 2' oc. The purlins are 1x4s, instead of my normal 5/4x6PTs, and also 2' ocI like overhangs as well. So for a building that is 8x12 with a roof that is 12x10 (ie, 4 foot and 2 foot overhang) how far would you space the rafters and purlins?
Looking at the photos you put up, it looks like you used 2x4s for the rafters and 2x6s for the purlins? But I can only guess your spacing so I can't figure out the quantity of lumber I need for my 12x10 roof. (the 12 foot is the part that will slope, so I'll need enough 12 foot panels to cover the 10 foot width)
I'm about to place a rather huge order and want to make sure my math/quantity is right.
My shed was 12x10 (roof) - I used 2x4s, set 2'oc. The purlins were 5/4x6PT ("Deck boards") also 2' oc. Like the goat house, its not intended to be walked upon. 2x6s would have been wiser.