Some examples include a fusing system for an additive manufacturing machine including a carriage movable across a build zone along the x-axis, a thermic source mounted to the carriage, and a roller mounted to the carriage adjacent to the thermic source. A longitudinal section of an exterior surface of the roller is exposed to indirect heat from the thermic source. The roller is controlled to rotate during and outside of a spreading operation of the build material. The carriage is to maintain the roller within a radiative heat transfer area of the thermic source.