Definitely read the ventilation article Aart posted. Rule-of-thumb would be you need 20 sq ft of ventilation in their - no small amount! And Lazy Gardener got her post finished before me
X2 on the upper AND lower vents! I'd do very large end vents at the peak of the gambrel roof since you don't have eaves to vent.
I assume in OK you get a lot of wind fairly often? Depending on if the prevailing winds can change directions (at my place they do - and wildly) you may need a lot more than 20 sq ft of ventilation with each vent having the ability to be shuttered so you can alter the ventilation pattern to keep full ventilation on the leeward sides of the coop regardless of wind direction.
You'll want the roosts midway between upper and lower vents so no drafts can find the roosts.
An unshaded coop isn't a problem if the have enough shade, shelter, and predator protection in the run. Just make sure it can cool off enough in summer evenings so it's not too hot in there when it's time to roost
Oh and make sure all vents are screened to keep our predators, too

I use 1/4" hardware cloth. It's not indestructible, but it's painful enough to defeat that most predators won't bother trying to deal with it. I would strongly recommend AGAINST poultry netting. It's good for keeping chickens in... and that's about it.
Good luck!