Note - I am only familiar with the RTs up until 2007. The early ones held up and are still going.
You can use any bat in cold weather. It is just you might be buying a new one sooner then you want. IMO, at the younger ages like some 12u, not all 12u ages, but at 10u and below. I really don't think it would hurt the bat. Just my 2cents.
IMO. A rocketech will dent quicker than most composites will break.
These Easton 777s will take a lot of abuse. The older the better and they won't break the bank. easton 777 fastpitch softball bat | eBay