If this is your first year with chickens or if you have children under 4 years of age, I would recommend getting rid of all of your roosters. I think roosters need some experience. First year people often times do not recognize the warning signs of an aggressive rooster. Roosters in my opinion take a bit of experience.
If you have had a flock for years, have mature hens, well then I would cull one bird, wait a bit and then cull a second bird. Roosters raised up in a multi-generational flock tend to be taught some manners by those older girls. If they are raised up with just pullets, you can get a nice rooster, but most often, they get bigger than the other pullets, and just become bullies and abuse the pullets because they are so much bigger. In just a hatch mate flock, I recommend culling the roosters or pulling them into a bachelor pad away from the pullets.
As to the roost discussion, (that you did not ask for) I would pull up the bottom, and make the roosts horizontal all one level, but lower than the ceiling, at about 25 inches below the roost. In SD, we do get wickedly cold weather (-25 to -30) I have never got frozen toes on round roosts, but I have had frost bite on combs. If the combs are too close to the ceiling, water tends to condense and rain down on the birds. They need a good air flow ABOVE their heads. Dry birds are warm birds.
