Dog, there is a cadre of very skilled rollers here in New Jersey, some of whom paddle regularly in Winter (I am not one of these people). This Winter they have been particularly active, both on the ocean and on our largest (and still mostly unfrozen) reservoir, rolling in water only a degree or two above freezing. Mind you, they come prepared to roll, planning to roll, expecting to roll; they are completely dressed for it with drysuits and thick insulating layers, gloves, neoprene helmets/hoods, etc., and are rolling by choice. But this can be a different story from being able to roll well, but being suddenly, unexpectedly capsized in icy water by some unplanned accident or incident.