I agree that the roosts need to be reworked entirely. They're too thin and would snap under the weight of the chickens. In the first picture, why do you have so much roost space so low to the ground, and just a tiny awkward board in the corner high up? Chickens want to be high up, they're not going to use that bottom roost if there are other areas higher up (like the nesting boxes). Roosts should be parallel to the wall, otherwise there's a lot of roost length in the corners that won't get used because it's too close to the walls. The areas of roost that they do use need to be much farther from the walls too, so they can maneuver and turn around on the roost. And to avoid them pooping all over the walls. If you're going to have two heights of roosts, they need to be staggered in a ladder formation with the lower one farther out than the higher one, so they can jump from one to the other. In the third picture, you have it backwards - the top one protrudes farther out than the bottom, so they can't use the bottom roost to jump up to the top one. They won't use the bottom one at all - it's almost touching the wall so no room to even sit on it, they can't use it to jump up to the top one, and they won't even try to sleep on it because the nesting box top is higher and more comfortable.
To make this better, I would switch to thicker roosts. I don't know what standard measurements of boards you have in Australia, over here in the US we have these common boards that are about 5x10 cm that work well for roosts (flat side down). Or you can use thick tree branches that are at least 8cm in diameter. Give them proper supports against the wall, too - something underneath the roost, either a large corner brace, or a block drilled into the wall (the metal walls will make this complicated, but that's one of the many downsides of a metal coop that you'll have to navigate). And place the roosts about 40cm away from the wall, at a height higher than the top of the nesting boxes. Give the chickens something halfway up that height, to help them get up there because not all of them will be able to jump up there from the floor (they might when they are nice and young, but think into the future - old age, injuries, etc.)
Your pictures have left out one of the most important parts of a coop - the ventilation! You'll need LOTS of it if you have a metal coop in Australia, to keep it from turning into an oven. The bare minimum year-round recommendation is 30 square centimeters per chicken, and you need a lot more in the summer when it's hot (or if you live in a hot climate). So, large vents protected from predators and weather, and lots of open protected windows as well.