Chickens like to roost as high a possible and it is common to see a game chicken 30-40 feet in a tree with their head tucked under their wings.
Chickens roost where instinct tells them they are safe. Remember how chickens evolved and try to think why they are avoiding the coop. Is the roof metal? Metal roofs are incredibly noisy during a rain storm. Or if an acorn drops on a metal roof the sound is similar to a rifle shot. Can you imagine trying to feel secure in those type of situations?
Another thing to consider is the ventilation. Chickens like fresh air. Make sure the air can move freely in your coop.
And believe it or not, chickens like a clean coop. Yeah, they poop all over but remember they evolved by roosting in trees. There is no problem with feces build- up when one is 30 feet in a tree. And there is no problem with fecal flooding when one can scout endlessly for snacks all over the place. Make sure your roosts are free of feces and mites. Nothing like trying to sleep with bugs crawling all over you.
Another thing to consider is your roost poles. Make sure the birds can access the roost without breaking a leg-some of the heavy breeds might appreciate a ramp to the roost area. Chickens with clipped wings definitely need a little assistance navigating high roosts. And make sure your poles can accommodate the size of birds you have. A large breed bird might not appreciate having to balance precariously on a roost designed for a bantam. My Jersey Giants like to roost on a 1 x 6. They especially like the top of the nest boxes which were left flat. But when I placed a 1 x 6 board higher than the nest boxes they have slowly decided to use the higher roost. Like typical chickens they were cautious of the possible wooden predator, but when the lower ranked pullets seemed to be enjoying the new roost the higher ranked hens slowly made their way to the new roost.
Don't forget flock dynamics when trying to solve the-not-wanting- to-roost-or-go-in-the-coop issues. Dominant birds might keep out the more submissive or the opposite could occur-the dominant birds might chase the submissive birds inside while they enjoy their outdoor freedom. Watch your flock and see if you need to add extra roosts, or take action against the bully bird.
While you don't need to build the Biltmore of coops, us chicken keepers need to keep in mind how these birds evolved. Make sure your place is not overcrowded, have plenty of ventilation, and supply plenty of different sizes of poles to accommodate the various needs of your chickens. While adding light to a coop to entice them in might encourage roosting, watch for bullying. You'll see a lot of fighting if your birds are in a tight space.
Once you feel your coop is perfect for your flock, start training them. I like to train by chickens from a day old on how to perch. Never hurts to have a secured stick on your brooder floor, and you'll be surprised to see the little guys trying to hop on the stick. As they get older you can raise your stick by securing however you want. As your birds mature you can continue to raise your roost. Years ago, I remember purchasing chickens who were raised in a small area with a wire floor and no roost. When I placed them in quarantine with a roost, they were terrified. At first I thought what stupid birds. Then I realized in their world that stick could possibly be a snake waiting to eat them. So I secured a roost to the bottom of the quarantine cage to allow them to check the stick out on their own terms.
You can also introduce ramps when they are young. They love zooming on those things once they learn they won't get eaten by the wood. When they are raised with all kinds of 'toys' or 'obstacles' using a ramp to get into the coop is a piece of cake. And the hens raised in this manner will teach their young by example. Since mom was desensitized to these things she will teach her chicks by simply doing these things. Just remember to supply different roosts and ramps for the youngster to explore.
When dealing with older birds-keeping them inside the coop for a few days will help. Once you allow them outside make sure to keep your food source in the coop, and don't leave food out free choice. If your birds are having difficulty navigating the ramp, sprinkle food along the ramp to encourage them to actually get on it. Remember, you are dealing with chickens, whose brains are the size of a pea on a good day, so you must be patient.
One of my favorite ways to get a new flock used to a new coop is to feed them only inside the coop. I'll feed them in the morning in the coop, and near dark I'll give them food in the coop-put the food near the door and sprinkle along the ramp and the floor near the door. I remove all roosts in the enclosed area to encourage the birds to go in the coop. And for those who just can't figure it out, I'll put them inside after dark.
Yeah, getting chickens to do what WE want them to do can be difficult. But sometimes thinking like a chicken is not a bad thing. Once our flock gets the idea the coop is a good place to be you should not have much of a problem.