Do not close the windows in winter. It looks like you really do not have enough ventilation as it is, allowing heat build-up in summer and moisture/frost build-up in winter. Most chickens (including RIRs) can handle cold weather, but direct cold drafts from the window is a problem. As long as neither window is facing the prevailing wind, they will be much better off.
As for the roosts, I'd recommend removing one and moving it so they are at least one foot apart. The total roost space is fine, but one roost will not be enough for them.
What are the interior dimensions of the coop (not including nest boxes)?
The common rule of thumb for minimum spacing of full-sized chickens is 1ft/bird roost space, 4sqft/bird in coop, 10sqft/bird in the run.
The fencing may be strong enough, but it definitely isn't small enough. Raccoons can reach through, grab chickens and kill them. Smaller animals- rats, snakes, etc can enter easily. The ideal is 1/2" hardware cloth which is much smaller and can prevent anything except mice and small snakes (annoyances only).
Although you mentioned it in your post, I recommend you add your general location in your
profile. Some questions (like this one) are location-dependent and that would be helpful.
Finally, welcome to BYC. People are very helpful here, so feel free to ask questions and people will be happy to jump in and help.