While you're adding roosts, might as well put one low enough for future chicks to use but not directly under the mature birds roosts (don't want them getting pooped on all night). It will strongly encourage the chicks to roost rather than lay on the floor and helps them further solidify their pecking order; as they age, the more dominant chicks will make their way up to roost with the others. This transition will help you in the decision process of who will be allowed to breed, who finds his way to freezer camp, etc. Since you're already adding roosts, it shouldn't be that much more work or expense.