I really get them in there much earlier. About 3-4 weeks. Do take them outside, as often as you can. Chicks really past a week old benefit from being cooler, and then being able to warm up. I often take mine outside for 15 -20 minutes in fairly cool weather, near 30 degrees. Then let them back in and get a good warm up, and they will take good naps, just like kids. Fresh air and sunshine are good for chicks.
And in your brooder have places, where it is much cooler, and places where it is much warmer.
As for your very lovely roosters... the problem with cockerels, their behavior today is no indicator of their behavior tomorrow or next week. It might not ever go south, or it might be a nightmare. Do have something set up so that you could separate them. And beware, sometimes very friendly rooster chicks, loose all respect for people, and have been known to become people aggressive. This board is full of stories where the darling becomes the nightmare, just beware, especially if you have small children.
They are flashy birds, you might be able to re-home one or both of them, if you have to...I know you are hoping and wishing, but that really does not work with chickens, and to be honest, two cockerels are about to become an awful lot for your pullet to take. Chicken raising is about tough decisions.
good luck, but plan for a way to separate the roosters from each other, or from the pullet until you have a lot more full grown chickens. Personally to have two roosters, I would want 25 chickens, but many on here have gotten by with less.
Mrs K