I don't grow this, but I did search around and it seems like you can prune it now. I don't think it is required to prune it, most people just seem to do it either to control size or remove and branches that died over the winter.

Here is a link that might be useful: Hibiscus

You will be able to tell which limbs are damaged. You can cut them off at any time. In areas where the trees are not always damaged by frost, they are often never trimmed. They grow to be small trees. I don't trim mine. The larger limbs are not bothered by cold weather, just the tender outer branches freeze. Now is the time of year to take cuttings if you want to.

However, others ofter cut them down to make them bush out in the spring. It just depends on the look that you want.

Here is some info from Walter Reeves.

Here is a link that might be useful: Confederate Rose

To get the confederate rose ready for wimter, I cut them back to the ground, just like I do my angel trumpets. Then I mulch ovrt them. When the weather gets warm, they start growing again. You can also cut pieced of the branches to root and make new plants.
Cookie

I have this plant also. Now is the time that I take cuttings and cut mine to about six inches tall, and add a thick mulch.
I clean up around the bottom of them too.
This past summer with the weather like it was I had some type of white harry bug on them....