Yes, on roosts higher than nests, but that's it they don't need to be any higher.That sounds fine in terms of distance from the vents. Not a lot of height for the roosts themselves though, chickens like sleeping up high. You can go another foot up and be fine with the vents. And make sure the roosts are higher than the nesting boxes, so the chickens don’t sleep in the boxes.
The more space between roost and upper venting the better.