The disclosure concerns a minimally-invasive medical instrument with a rotatable inner shaft mounting a medical tool. The medical tool may be, for example, a forceps, a grasper, a cutter or other medical tool useful for therapeutic or diagnostic procedures. The medical tool is desirably used in endoscopic, laparoscopic or other minimally-invasive procedures. The jaws or other end-effectors of the tool are operated by a first control wire, which will act to open or close the jaws or other end-effectors of the tool. A second control wire is used with a camming mechanism to transform linear movement of the second control wire into rotary motion of the inner shaft, thus also rotating the medical tool. The medical tool may thus be oriented at the surgical sit as desired by the surgeon, by rotating the tool without having to remove and re-place the tool within the patient.