The roosts is easy to answer. Why would roosts be only on one side? I see reason they wouldn't be on both sides.
The cleaning is more difficult. I think it depends on how big the coop is.
My coop is divided into a front section and a back section. Both sections have doors but the door to the back section is very securely covered with metal lath (which is essentially a wire mesh), so people can't get through it. I park a wheel barrow in the front section then stand in the back section to shovel the bedding into the wheel barrow through the sliding door in the divider fence. I think it works well. If I didn't have deep bedding and had to clean it out more often then I think a shovel would work without the wheel barrow - like the cat litter scoop works for the poop board.
If your coop isn't big enough to stand in while you shovel, you might be able to stand in one half while you shovel out the other side. You might try it out before building... maybe put some boxes in a row or hold some plywood with saw horses in the same size of your coop then try moving the shovel around to see.
Obviously, if you don't have a door in middle wall, you would need a door to each side.
The front "window" isn't really a window. Instead of a wall, you cover it with fence wire of some sort. Here, it needs to have small openings to keep rodents and predators out. Yes, it stays open all the time, even through snow storms. Not much snow comes in because the other walls are solid - the wind doesn't blow the snow in because the wind has no way to go through.
The top window (the monitor window or clerestory window) is open all summer but not in the winter. How much rain comes in depends on several things. Some of the things are how far the roof extends past the wall, whether your windows hinge out to protect the opening (or are taken off completely), how consistently your weather comes from the other directions. In the summer, it doesn't matter much if some rain comes in - in my climate at least. The coop has enough ventilation to dry quickly. My climate is generally humid but not like a rain forest.
My coop gets more rain in it than the Woods' style in the links. I had to compromise with family members who wanted it to look like a standard shed. So I have the entire side open instead of the lower roof sheltering some of the open side and I have no upper windows to open out to shelter it more.
