Some steel bending projects require the equipment and expertise from what might be called different disciplines within the bender/roller world.
A recent example involved a large beam stringer for a spiral staircase. It required W24x84 wide flange beams over 45′ long. Most stair stringers are made from small to medium sized channels, plates, or tubes that are rolled on plate rollers. Your typical stair stringer roller would probably not have the machinery to curve such a large and long beam.
On the other hand, while the typical large structural beam bending shop might have the equipment, they would not necessarily have the experience and knowledge to check that the stair stringers are made accurately. Such a job requires a bender roller whose expertise covers different types of rolling. Only a shop capable of doing work in these two disciplines could give the customer the confidence that the parts would be made accurately and quickly.