My chicken house has a shed roof, meaning one slat that's tall in the front and tapers down in the back. I don't have any current pics right now, but found a construction pic in the files here to show. It's plywood covered with tar paper and leftover asphalt roof tiles from my house, and they sit along the front edge with their toes over the front for balance. I've never had a problem with the roof and their feet, other than when trying to clean the poop off.
I did have a big limb fall that I put up there for them to roost on if they felt like it, in case they wanted something other than the edge to sit on.
It looks like yours don't sit at the peak but are more at an angle. If their feet look ok, they're probably ok. If you really wanted to cater to them, you could probably add a limb or roost up there that's at less of an angle. Otherwise I'd think if they weren't comfortable they probably wouldn't go up there.
As far as light and ventilation, that may certainly help. My house has a large always-open (and hardware cloth screened) window that faces south for maximum light, the whole front door is either screen in summer or covered with plexi in winter for more light/vent, multi vents on the side, and their access door is always open. They still prefer the top. I think it's a height thing. Chickens will always try to roost in the highest protected spot they can. The day my dad delivered the house and we turned the chickens loose in the coop to see it, the first thing they did was fly on top and hang out there.

It looks like yours don't sit at the peak but are more at an angle. If their feet look ok, they're probably ok. If you really wanted to cater to them, you could probably add a limb or roost up there that's at less of an angle. Otherwise I'd think if they weren't comfortable they probably wouldn't go up there.
As far as light and ventilation, that may certainly help. My house has a large always-open (and hardware cloth screened) window that faces south for maximum light, the whole front door is either screen in summer or covered with plexi in winter for more light/vent, multi vents on the side, and their access door is always open. They still prefer the top. I think it's a height thing. Chickens will always try to roost in the highest protected spot they can. The day my dad delivered the house and we turned the chickens loose in the coop to see it, the first thing they did was fly on top and hang out there.