Since they have just started to roost you are way ahead of the game. They are living animals so you can never be absolutely sure what they will do, but there is a 99.999% change they will want to go back to the coop when it gets dark. That’s about as sure a thing as you will get with chickens. Don’t even worry about them wanting to go back to the coop. There are a couple of things that might happen though.
Chickens have no concept of gate. Their bird brains just can’t grasp that concept. I’ve had mine desperately trying to get through a fence to get back to the coop at night but totally ignore the open gate they have been using all day to go back and forth. Most of them do make it back but I’ve had to guide a few to the gate one or sometimes two nights before they catch on. I wish I had a video of that, it’s hilarious to see. So depending on what your set-up looks like, you want to be out there at bedtime to watch them go to bed. Most of the time they do fine, but occasionally you have one of those that needs help.
Since yours are going from the pen into the coop at night already to roost, this one is probably not going to happen. Sometimes instead of going back into the coop they huddle together just outside the coop. You need to put them inside physically after it is dark enough they are easy to catch. If this does happen, it will be right at the coop. For some reason known only to their bird brains they don’t always actually go inside, but they will be at the coop. So again, check on them at bedtime.
A handy trick is to teach the chickens to come to you. You need to be consistent but choose a container, (bucket, bowl, something) and use it to feed them treats, calling “here chickie, chickie” or something appropriate as you rattle the treat in that container and feed it to them. As long as you are consistent to do that whenever you feed them treats it usually doesn’t take long for them to come running whenever they see the container, hear it, or hear you call them. That can be really handy if you want to get them back in the pen during the day.
You don’t have a rooster, you have a preteen cockerel, just a little boy. In the next few weeks you should see some major changes in his behavior as he goes through adolescence and becomes a true rooster. Your little girls will grow up too. Fasten your seat belt, that can get exciting while they go through that transition.
Will they stay together? Probably for the most part. When you first let them out, just open the gate and leave them alone. Don’t try to force them out or anything like that. Chickens often don’t like change. It’s possible they will rush outside and immediately start eating grass and chasing bugs, but it’s more likely they will be afraid of the great outside. They might just stand at the gate and look out there, curious but scared. In their own time they will venture out and learn to enjoy the great outdoors but don’t rush them. They can manage that on their own. There is nothing wrong with them if they are cautious.
When they first go out they will probably stick very close to the pen, the area they are familiar with. As time goes by they will become more comfortable out there and start roaming. They may stick to their general area or they may go several hundred feet. With a flock your size don’t be greatly surprised to see some of the pullets form their own sub-flock and go off on their own at times. That’s perfectly normal as adults. During the adolescent phase you are likely to see pullets avoiding that cockerel in various ways. Each flock has their own dynamics and ways of dealing with things. Normally they work through that phase and everything is calm and peaceful but adolescence can sometimes be turbulent.
Good luck! Sounds like you are doing great.
Thanks!!
and the light is on. They just last week started to roost instead of sleeping on the ground Well I will try letting them out 
