What type of hull typically rolls without a deep keel?

A round bottom hull is characterized by its smooth, rounded shape, which allows it to be more stable in calm waters but makes it less stable in rough conditions. This type of hull often rolls when there isn't a deep keel to provide balance and stability. The round shape enables it to cut through the water efficiently, but it also means that without the additional stability from a deep keel, it may sway or roll side to side, particularly in choppy waters or when there's a shift in weight on board.

Flat bottom hulls tend to be more stable and less prone to rolling because of their wider surface area in contact with the water. Planing hulls are designed to lift out of the water at higher speeds, providing a stable ride on top of the water rather than rolling. Multi-hulls, like catamarans or trimarans, are known for their stability due to the large beams between hulls, further preventing rolling. Therefore, the correct choice, round bottom hull, stands out due to its inherent design characteristics.