If you have an all hen flock, and the rooster is more than 8 months, this is the EASIEST introduction made with a single strange bird into an established flock.
The rooster will strut in, one or two of you more dominant hens may try to bluff him, and by tomorrow morning, they will all be in love with him.
It will change the dynamics of the flock, the hens will no longer look to you, but rather to him. Feed him, he will call the girls over. Kind of neat to see.
If the rooster is young, he will not be a flock master until he is nearly a year old, he should be dominant by the time he is full size. If the rooster comes from a multi- generational flock (with older hens and another rooster) he will understand chicken society, but may be intimidated for a while by the older hens. They may teach him some manners.
Good luck,
Mrs K