Depending on how many rats you need a week you can determine how many pans you need.
For feed a collection of ~ 150 snakes almost exclusively out of an 8x10 "barn". Occasionally we buy mediums to feed the bigger girls when they are building because we have no room for grow outs. But this is what we do and you can take from it what you would like.
We harem breed 7-8f per 1m they stay together for 21days then the females are removed and put in individual brooding bins. Then the next set of females is moved in with the males. The females give birth and we pull the pinks down to 12 and feed or freeze the excess. The next week we pull pups down to 8, feed the excess. The 3rd week when the female is ready to return to the rotation the pups are able to be weaned and are fed off while some are kept for breeding. Then do it again. The secret to success is consistency.
Feed a high quality diet rodent diet (we feed Zeigler), keep them in fresh water and clean bins and make sure to change out your females every 8 litters or so. Males are changed every spring so we have young virile males for summer and we don't lose production.
Every thing is kept in an outside shed with ventilation of a screen/hardware cloth door and a vent fan. In the summer we have a big fan that blows across the racks to keep them cool and we will spray the outside of the shed and roof if it gets really hot. We are in FL.
We used to feed Mazuri and keep males and females together all the time but we have almost doubled our production using the new food and harem breeding methods. We pull 100-120 smalls every week.
Hope it helps. Good luck with your rodents!