This is what I have found too. My girls are much happier with roosts at the same height. So if your perpendicular roost does not work. Make a new roost at the same height as the highest roost.
However on closer looking, your roosts are pretty low (some people like them that way as they worry about heavy breeds and legs) so if that is what you want - good and well.
However, it appears to be a ledge above the roosts on both sides. There is a lot of space up above them. I think it would be easy peasy, to put roosts across the narrow width of the coop on the ledge. And you could 3 -4 roosts about 24-30 inches apart.
Everyone is at the same level, and hens can move to a different roost out of reach of a pecker.
The other way I have added length to a roost, is to run it not parallel to the wall, but rather kitty corner or on the hypothesis, which is longer than the length of the coop. From say the NE corner to the SW corner.
Mrs K
