According to a book I have...
Roosts: If you use traditional stair stepped roosts, you should set the bottom perch about 2 feet from the floor and higher rungs an additional foot apart. 2x2 boards make ideal roosts for full size chickens. The book states you should not use plastic or metal for perch material.
Nest Box: A 14 inch wooden cube with one open side makes an ideal nesting box for full size hens The book says as long as the cube is bigger than the chicken, it should be fine. they state the cube should be placed in the darkest corner of the coop with one nest box per four hens.
I hope this is helpful. Good luck. Show us pictures with what you come up with.