1: do all chickens roost??
2: if I put roosts at different heights will all the chickens just go to the highest ones?
3: if I have different breeds of chickens do they require different size roosts at different heights?
4: what is the highest you want a roost from the ground?
While some individuals are oddballs, as a rule, chickens roost. Some breeds, such as Silkies, can't fly up to a roost and other breeds, like Brahmas, are too heavy to fly well and need lower roosts so if you have those birds you'll need a ramp up to the roost like the one I have here to let my Brahma reach the roosts and the nest boxes:
Alternately, you can use a ladder-style roost so that the chickens can hop from rung to rung.
Most chickens will roost as high as they can get but if the top roost is crowded the dominant birds will force the low-status birds off.
As long as the roosts are higher than the nests they can be placed at whatever height is convenient for you. My nests are at my elbow height so I don't have to bend down to collect eggs and my roosts are at my shoulder height so I can pick birds off of them to do exams, etc. conveniently. If you don't have a bad back that's not important.