I've had Wyandottes roost in rafters 10-12 feet above the floor, so you can probably cross the concept of "roosts that are too high for the chickens" off your list of worries.
There's a tendency for roosts to get hugely in the way of chicken management, because they tend to block off a big percentage of the coop, and people are rightly reluctant to put stuff under the roosts. Without droppings boards, anything under the roosts gets bombed with manure; with droppings boards, you have to deal with droppings boards. Either way, access to the stuff under the roosts is compromised.
Probably, by now, every conceivable solution has been tried! I recently came across a picture of a feed trough that pulled out like a drawer for refilling, so it was tucked under the droppings board while in use, but out in the open for filling.
Another method is to partition the coop into two parts: the chicken room and the human room, with access to the nests and feed hoppers on both sides of the partition. Both ideas solve the problem that the roosts overhang the equipment and make access difficult for humans. A halfway version of this solution is to provide access to the feeders and nests from outside the coop,which sounds great when you imagine a pleasant fall afternoon, but probably not so much with wind-driven sleet.
On the whole, I'd recommend roosts at 4-5 feet off the ground if you need to put things under them. That lets you duck under them if you need to, without making them so high you can't get at the hens when you need to. But I'd arrange it so ducking under them isn't something you have to do routinely, but only if there's an egg or a sick chicken in the corner. You might consider putting a slanted roof over any equipment that's under the roosts, rather than droppings boards stretching across the whole area. There's two schools of thought about droppings boards. See my
droppings board FAQ.