If I had to hazard a guess without Googling the answer, I'd say it's similar to the effect that makes a curve-ball curve. The relative airflow over one side vs. the other due to the rotation of the cylinder (or ball) as it moves through the air generates a pressure differential that can be used for lift.
Changing the rotation rate of one side relative to the other would provide different lift on one side, allowing you to bank into a turn. I'd think some additional control surfaces for banking would be preferable, however. Overcoming the angular momentum in the rotating cylinders to change their speeds quickly enough to be responsive would be quite a challenge. The model in the video appears to have a single axle to drive the cylinders, and uses rudder for turns.
Quite an interesting and unique concept.