Hi there! From what I've experienced, once you are certain that some chicks are roosters, at around 4-6 weeks, then I would (and have in the past) cull them then. A few reasons would be because it will save you some on feed costs, and it's a sure way to make sure that your hens and established...
We have a 5 yo Pyrenees, and while he's a great dog, he is very prone to chase around our flock, but he hasn't killed any chickens (knock on wood). He is very stubborn, but still protects our flock well. We have him on an e-collar for an invisible fence, and that works wonders for him knowing...
When I was younger, my dad bought my mom 6 chicks from tractor supply about 8 years ago as a surprise Easter present, and since then, chickens have been my favourite creatures :) I'm now 18, and our flock has now grown to a dozen, mostly backyard mutts (maran and easter egger mixes). My...