Cockrels, and all chicks, will spar to establish pecking order. Do you have plenty of room for them? What breeds? Game breed cockrels will injure each other and need early separation. Other breeds should do fine, but if there are any injuries, things need to be rearranged. Mary
You're sure they're roos? Pullets will do the same thing in the brooder (jumping up, chest bumping, jumping on backs, etc.). In either case, enlarging the brooder and giving them other things to do can cool them off a bit.
They probably do need more room waiting to put them out in coop but the weather here just did a 360 ones an Americana an ones a bantam I'm assuming they are Roos because the comb on top is slightly bigger than the rest