Also check the coop for parasites that might be causing discomfort. Red roost mites can live in coop crevices coming out to feed at night. This can make the birds miserable such that they don't want to roost in the coop. Check by going to the coop at night and flashing a light on the roosts and in the corners. Mites will be slow moving grains of pepper. If you find them, clean coop thoroughly and treat all birds and coop with poultry dust or spray, repeat in 10 days. Mites can be wicked to get rid of.
Sometimes a lower ranking bird will simply choose to roost outside and others follow. I've had to place them inside the coop until they settle whatever pecking order issue is prompting.
Finally, you might want to double check the space and make sure all birds have adequate roost space.
My suggestions.
LofMc