In my experience, roosters need more space than hens. And pullets with a young aggressive rooster need hide outs, different levels in the run, roosts and hide feed bowls.
If they are all the same age, then you might have trouble, when the hormones start raging. Do come up with a way to pull your cockerel out of the pullet flock if he bothers them too much. Often times they get bigger than the pullets, and without older birds to thump manners into them, they can become a bully. A dog crate, can give the girls peace.
If you can remove him, permanently, it often times is a good decision. An all hen flock is a nice way to start this hobby. Roosters take experience in my opinion. They can become violent and aggressive, regardless how you raise them. Many inexperienced people vastly underestimate just how violent they can be.
Mrs.K