We can't keep roosters here but we had them when I was growing up. We kept the roost up high in the coop so they couldn't stretch their necks to crow. If my recollection is right it worked on some but not on others. Plus roosters crow for pretty much unavoidable reasons. Any light, or rather an increase in light, seems to set them off so won't the amount of light let in by the necessary ventilation set them off to crowing?
How old are your chicks? Some breeds don't roost until they are older. In our case, once one of them did it the others quickly followed, imitation seems to be how they figure out most everything.