<p>Roll reduction system for rotary steerable system. A well drilling system includes a tubular housing that attaches inline in a drill string and a bit drive shaft supported to rotate in the housing by a roll reduction system. The roll reduction system includes a first gear carried by the housing to rotate relative to the housing and coupled to rotate with the bit drive shaft, and a second gear carried by the housing to rotate relative to the housing and coupled to the first gear to rotate in an opposite direction to the first gear.</p>
