Yep, that was all the bobbing and weaving that he'd use to dodge punches and to get closer. I remember reading about Archie Moore giving credit for Dempsey's bobbing and weaving that he'd use in own style. I'm sure that the shoulder roll was no exception.

I like the fact that Dempsey almost always had good leverage for his punches. When I think about it, I'd put the Dempsey-roll is in the same category as the shoulder roll. The beginning position is essential. For starters you duck/roll away from the punch, you shift your weight onto your left, getting set to punch with your right. It's not a big difference to duck under it, or roll away from it as long as you're in position to come back with with your own punch. You can also hook off it as long you shift your weight back to your right leg.