rotational dynamics - Torque from Gravity

If a sphere rolls on an inclined plane, why does the component of gravity parallel to the plane not exert a torque on the sphere? Shouldn't infinitesimal mass particles experience a force of (dm)gsin(theta)? Because infinitesimal mass particles experience the force at different lengths, shouldn't they experience torques and, consequently, give rise to a net torque?

I ask this question, because the following link (starting at subheader "Perspective II")

treats friction as the only torque-contributing force applied to an object on an incline.

http://physics.bu.edu/~duffy/sc527_notes06/race.html