My Cochin can jump up to my 30 in high poop board, but she has trouble getting from the poop board to the actual roost, which is 12 inches above that. So every night, I put her up on the roost so she doesn't get pooped on. She's such a big baby... I imagine that if I set the roost further back from the edge of the poop board, she'd be able to manage just fine. But I'd have to remake the whole poop board/roost set up. Not gonna happen!
I have a ramp that she uses to get down from the roost, but she won't use it to get up there.
Bottom line, your Cochin can probably navigate fine, as long as she isn't a big baby like my Iris.