The only reason you have to have a rooster is if you want fertilized eggs. If you want unfertilized eggs, you cannot have a rooster with the flock. They will lay just as many eggs without a rooster and sometimes one of the hens will take over some of the duties of a rooster, things like watching for hawks and breaking up fights between the hens.
I don't know what trouble you know you will have if you introduce a rooster later to a flock of hens. It is true that anytime you introduce a living chicken to another flock, you take a chance with diseases, but people successfully introduce new chickens all the time. They are living animals with their own personality, so anything can happen. There is usually less trouble adding a rooster to a flock of hens that adding another hen, if the rooster is mature enough to sway the hens with the force of his personality and the hens are mature enough to accept him without running away. Sometimes he has to forcibly take the dominant position away from the dominant hen, but that depends on their personalities. Some hens never accept a rooster's dominance, whether they are raised with them or are introduced later.
If you introduce an immature rooster to a flock of mature hens, there is a good chance the hens will not accept him or submit to him and will pick on him mercilessly, much worse than if you introduce a new hen. He has to be mature enough to enforce his dominance by his personality. As always, it depends on their individual personalities. Some flocks of hens will accept a young rooster and sometimes a young rooster has a strong personality. Nothing is guaranteed.
If you raise a rooster with the flock, you often have to go through that stage where the rooster and the pullets are adolescents. The rooster is full of hormones and knows what he wants to do, but maybe he has more urgency than technique. The pullets are not mature enough to quite know what is going on so they resist, even if they have started to lay. The rooster, in his urgency, gets violent and tries to force himself on the pullets. Usually they outgrow this stage, but some roosters remain brutes and some hens never learn to accept any rooster. It is a case of either the rooster not having a strong enough personality to dominate or the hen having a personality too strong to ever be dominated.
Usually introducing a mature rooster to a flock of mature hens is the easiest integration possible. The rooster establishes his dominance by mating with the hens, the hens accept him, and it is over. But it does depend on the personality and maturity of the rooster and hens.
Many people have roosters for reasons other than just fertile eggs, but getting fertile eggs is the only reason you have to have a rooster. We all have different goals for keeping chickens. My normal advice about roosters is to keep as few as possible and still meet you goals. In your case, that may easily be no roosters.
Good luck!!!!
