I find introducing them when they are free ranging is the best.
Then they have space to run away from each other.. and are not able to get cornered in the confines of the coop.
The roosters will fight when they first meet. Be there to keep watch..... If they have spurs file them down to make them blunt or stick something on the ends of them to make them not sharp.
Just let them fight and the looser will run away and then he knows he is rooster number 2 and won't challenge the winner.
This works most of the time.
However, sometimes you get a crazy rooster that will not accept being the looser.. and even through he gets beaten up every time and chased away he will keep going back once he gets his breath back for another fight. If that happens you will need to keep the roosters separated.
Make sure when they are fighting the first time you split them up if one seems to be very tired.. and can't get its breath. The fight should only last a few minutes.. any longer than 5 minutes is going to cause them too much damage. Don't split them up unless you see one is getting hurt badly..
Also, usually there is a lot of blood.. but this is from the roosters combs... they peck at each others combs. The combs heal up really fast... that is one thing they are designed for.
Be extra careful when they are going into the coop to roost. Make sure there a lots of places the looser rooster can hide and get out of sight of the boss one.
Finally, NEVER just have the roosters separated through mesh. They will fight through and mesh and really mess up their faces and eyes. This is because they can't fight properly and pin the other one down.. so they just keep pecking and pecking each others faces through the wire and will get serious injuries.. even loosing an eye.
Keeping them, as some advise, in separate cages and gradually letting them get used to the sight of each other DOES NOT WORK.. it makes the aggression worse... as the rooster want to fight and can't get to each other.. so they get super frustrated and when they finally do meet outside they will really hate each other and fight harder.
All roosters are different... keep a close eye on them.. and be prepared that they may never be able to live together.
Good luck.
and Welcome To BYC! X2 To try to get them to get along, would just use the same method you generally use to introduce new birds, to have a long period of the two flocks being able to see each other but no touching, through wire seem to work best, ie dividing the coop into two sections or keeping the new/younger ones in a cage inside the coup for a couple of weeks to a month at least. The chickens will get to know each other and sort of work out a pecking order before actually coming in contact with each other. After a week or two, letting them free range together is a good idea and should help... It will take a couple of weeks to get the pecking order sorted out. There is a nice article in the Learning Center on integrating flocks you might like to check out, the part about actually combining them is after the quarantine section https://www.backyardchickens.com/a/adding-to-your-flock But RIR roos (especially hatchery ones) have a reputation of being pretty aggressive, so you may not be able to get the two boys to live together in peace in the same pen with hens to fight over, so you might want to be prepared to have two flocks.
