I have a stag pen. Boys who are raised together may or may not get along well in the long run. It's a complete individual thing and there is NO time limit! My boys raised together were fine until suddenly one day around 10 months old they were not and one boy was hell bent on giving the other a beating no matter how far he tried to run and hide. It was relentless. Step in me and give the chaser a chase of my own, because I do think the best defense IS often a good offense. After that it simmered down for the day, yes with plenty of blood and a swollen eye. They were fine together after that until the end. And I also put boys who were NEVER raised with my main roo into my stag pen. If done before hormones hit the new additions AND as a group, not too much of a problem. Bit more of a problem if I try to add an individual adolescent. That day, no extra amount of females, space, feeders, or hiding spaces was going to stop the aggressor. The victim was already on the cull list for the next day, but I couldn't emotionally justify it after his beating. Figured I would wait until the next cull session. In the end the victim got the last laugh.. because somebody was looking for a boy to service their ladies (short term) and since that guy didn't fit my program I let him go. My keeper is still in the stag pen with my new rounds of boys, but the other guy got to spread his seed to 10 lovely ladies for a couple of weeks before his quick end came.
I'm guessing that even though life is pretty good here, he probably died happier!
Those folks only wanted some hatching eggs for their broody. And the gal deeply hates the idea of eating fertilized eggs. They said they were very happy with his service.
Anyways, what I'm trying to say is that current aggression, especially at this age does NOT dictate future aggression... because hormones do crazy thing to people and yes, animals.
Side note regarding roosters... they are territorial animals. And so yes, they might be able to have their own harem and maintain their own place on the property avoiding each other... The ONLY boy that ever attacked me was the friendliest EVER cockerel. Once he started attacking he KNEW he wasn't allowed in my space. It was fairly comical to see him come into my claimed area the MOMENT I left and start crowing and all. Then when he saw me coming he would high tail it towards the gate that I would open and let him back into HIS area.
I agree with MaryZoe, roosters aren't all bad... they can be a lot of fun. And there are reasons to keep one if you desire. NOT protection, most of the time IMHO... as roosters simply are NO match for things like raccoon, domestic dog, mountain line, coyote... you get the idea. They often just become the sacrifice. And my hens EASILY are on the look out for hawks and the like. But EVERY situation is different EVEN at my own house and we all have individual thoughts, and likes or dislikes.
I agree with the other poster that said RIR have the reputation of being bullies. It MAY be a stereotype, but I hear it quite often. If I was keeping him for protection or hatching.. I MIGHT keep the red as their egg laying should be superior to the WY. However, it is my understanding that Wy's are good eatin'. (yes the two we ate were plenty tasty also), doesn't seem like your quite at that point though. So I would weigh your goals along with the info you have and make the best decision you can for now.
They are too young to be showing any real aggression yet, though some are very clearly jerks from the get. It is usually the kids that are gone after first or the dogs. Just not worth the risk. Maybe unless you aren't free ranging. And even then there may be a day come when the hormone switch tells that boy that you are a threat and suddenly get flogged while collecting eggs. 
