You could just stick to two roosters or even one and then have a pen for breeding. When you decide to hatch just put the chickens you want to breed together, wait two-three days. , collect the hatching eggs and then put everyone together again.
According to the recent issue of Practical Poultry. "When a cockerel is put in a pen, fertile eggs will follow as soon as the second and third day." I wouldn't think three days is enough to upset the routine of the flock. Then you could simply collect only those eggs of the hens in the breeding pen and hatch them.
Further is says. "If he's replacing another male, eggs fetilised by him will be laid in a couple of days, those fertilised by the previous male will continue, but only for about a week."
"When a male bird is removed from the breeding pen, a good nuimber of fertile eggs will be produced for a further week, falling to around 50% by day 10, and on down to 10% after three weeks; a very low percentage may even be found up to the 26th day".
Hope this helps
All the best
Rancher
