Its not a big roof---------------------it will cover the dresser that is my avatar and extend a bit past it to the side and to the back ------I am opening the back of the dresser to make a back deck in the coop.Yea for 1/2" plywood your rafters should be 2 feet apart, no more or you will have problems with sagging. 3/4 you might be able to space a little note but I wouldn't recommend it. Did you look into a metal or plastic roof?
I cant find good simple pictures of how to make a lean to roof.
Honestly I was just going to have 4 posts on each corner--------------but now given what you say I am not sure..............
I don't know "rafters or trusses " etc...............I have watched a few shed building you tube videos ------------honestly they are still too carpentry advanced for me...............
I did not look into metal or plastic------------because I have been trying to use materials I have or can find via freecycle or craigs list.
I don't know how to cut the corrugated plastic or tin............also................
I do searches for materials yet find I may not be using the correct materials or roofing lingo............UGH............its hard to be such an amateur!