I run two 55 litre tubs in the garage and only keep a take away container inside of small ones for feeding out of each day to baby skinks.
On really hot days I have had some large death rates but they build up again fast. No way am I bringing the full colonies inside as they do stink.
I feed them dry dog food, carrot or pumpkin and any other scrap veggies.
You don't need to separate the young but if you need small ones to use for food, this is what I do.
Get a take away container, paint Fluon or Vaseline around the top, place the container in your colony tub and cover with a piece of small gauge wire mesh. Shake an egg box of roaches over it and only the small ones fall through the wire.
Then if you want to clean out some off the garbage in your take away tub without loosing the little roaches make a lid with fly screen, turn the container upside down over a bin and shake.