What breed is the roo and what breeds are the hens? I've got some info on roosters here:

http://jackshenhouse.com/VSChickRoosters.htm

And when adding ANY new birds, I use the 'Meet & Greet' technique, here:

http://jackshenhouse.com/VSChickIntroducingNewBirdsToFlock.htm

There is no avoiding a certain amount of pecking, they need to establish the natural order within the flock. I never remove my roos at night, me entire flock stays together 24/7.

Remember he's really still a youngster at only three months old--the hens will treat him as they would ANY new youngster--with pecks. He should grow into his roll.

Velvet ~:>

Thanks for answering so quick... unfortunatly, I went out just after I posted to put him into the coop with the sleepy hens and he was GONE! I assume he went to find somewhere to roost for the night because he is used to free ranging and I don't think he was impressed with the pen. But there is a fox hanging around in the field so I hope he didn't stray too far.
I was thinking, if he doesn't return, would it be better to get a rooster who is full grown and can fend for himself or should I just wait until next year when I replace my layers and get everybody at once so they are the same age and can grow into their roles. I want a rooster to protect the girls so they can free range in my yard.

The Prodigal Son has returned... YAY
I thought he might.

Barbie--

My Egglebert was three months younger than the hens, and he was so intimidated by them when they first met! But now he definitely rules the roost.

Give your boy a little time and they'll work things out.

--Johanna

I have named him Earl.
He is a Sussex so I thought Earl of Sussex would be appropriate. And, if he turns out to be nasty I will be singing "Earl had to die" by the Dixie Chicks. ; )

Aw, the girls were irresistable. :)

Velvet ~:>