Can you prune knockout roses before they are a year old or do you have to wait?
Pruning Knockout Roses
You can prune Knockout roses if you need to do some shaping pruning. They will do fine without deadheading pruning. I just prune them up a bit as needed for shaping and removing dead cane material in early spring once they form leaf buds. That way I know how much is truly dead. Here is a link to an article for you too: https://www.gardeningknowhow.com/ornamental/flowers/knockout-roses/prune-knockout-roses.htm