In a hypothetical fight between a Rottweiler and a pit bull, the Rottweiler is a clear-cut victor. Both breeds are muscular and stocky, but the Rottweiler's considerable size gives it the advantage.
An average male pit bull ranges between 40 to 90 lbs depending on the particular lineage of the breed. The weight standard for a male Rottweiler is 95 to 130 lbs. Rottweilers are working dogs and benefit from high-energy, high-endurance jobs like field, farm or guarding work. Pit bulls were bred from Staffordshire Bull Terriers for the original purpose of dog fighting and bull baiting.
Both breeds are considered "dangerous breeds" and are banned in certain cities and apartments because of their high bite records, but the number of recorded pit bull attacks on humans greatly exceeds that of the Rottie. This is simply because pit bulls are a breed that is much more commonly bred and kept, not because of the breed's so-called vicious nature.
It is worth noting that both the Rottweiler and the pit bull are also widely recognized as lovable family pets in a properly trained environment. Dog fighting is an illegal practice that is harmful to not only the dogs involved, but to breed perceptions as a whole. The dangerous stigma that is common to both breeds is the primary reason Rottweilers and pit bulls are some of the animals most commonly found in shelters.