I would love to see how you incorporated the ladder. I've got a silkie that can't make it to the top roost so has to sleep alone on the bottom one every night. I went to a lot of trouble to renovate so I could make the roost longer so she could fit up with the others so that is a bit of disappointment lol. With winter coming I've been wondering how I could get her up with the others.
As for flying our australorp years ago was a real escape artist, and we ended up with a 8' fence to keep it in. It only ever escaped into the re back yard from their run though. Wasn't interested in jumping the 6' fence the other direction.
Two 1x4x8 at least as long as the distance between the roosts placed parallel. Dowel rods screwed in to form "rungs." Screw to roost.

You can have as many rungs as needed that way.
MrsB