Most of mine will Play Big Chicken and roost on the roost bars (branches) during the day, but at night they're still content to pile up in the Dead Chicken poses on the floor of the coop. The only YOUNGSTER who learned to roost at night is my first GrandChick, Samanatha, hatched by broody Buffy. Buffy taught Sam to roost. If Sam wanted to be next to Buffy at night after Buffy got tired of spending her nights on the floor of the A-Frame "Broody Mansion" coop, then Sam darned well better learn to jump to the roost and stay there all night with her.
All the other "me-raised" chicks didn't actually roost on the bars at night until they were around 16 weeks old. Samantha was on the roost bar by 9 weeks.