Q.Can i prune a desert rose that has been frozen?
I forgot to bring our plant in during a recent frost – can we prune it back?

How badly was the plant damaged in the frost? Since the plant's exposure to the cold was seemingly short, the roots may not have sustained damage since they were insulated by the soil. You should prune away any leaf or stem issue that is discolored from being frost bit. The plant might perish if the bulbous lower stem gets soft and mushy.
For more information about saving cold damaged plants, please visit the following link:
https://www.gardeningknowhow.com/plant-problems/environmental/how-to-treat-frozen-plants.htm