OK... how old are your chickens? I have some brooder babies that are only just learning to roost. I think when they have a Mama chicken that teaches them to roost, they do it faster. I had to put some of mine up on the roost so they'd know what it was there for. Once a few started, they all started. Some birds, like silkie will roost on the floor, or on very very low roosts. I however have a silkie who roosts 5 feet up, and his lady love, she roosts on top of the nest boxes. I have front open nest boxes not top open, so poo is not a problem... I also have some that roost in the uppermost places that you'd think they couldn't get, but they do... They may also prefer to roost in the door of the coop if the location is cooler, better air... I have a summer coop. Only a few birds actually use the enclosed coops this time of year. By summer coop... I am in Michigan. This summer has been uncomfortably hot. I took my winter run, added half walls just at the tops of the run are to keep the wind from hitting the birds, and the bottom of the walls are 2 layers of fencing, and then a layer of plastic net, 24 feet of roost space. I put a few birds up there one night, and with in a week, ALL the birds from the 3 different coops discovered it, and have not been back in the coops all summer, the coops are just unbelievably hot even with the doors open, vents and fans... If your run is secure, predator safe, and I do mean SAFE, top covered and apron-ed... Then why not put roosts out in it, then move them back into the coop in the cold months... Just a thought.