I assume the ball was rolling when it encountered the incline. If the
incline is frictionless, there can be no torque on the ball so that the
angular velocity of the ball can't change. Thus the kinetic energy that
is in rotational motion can't change. Thus as the ball rises and gains
potential energy, all of that energy must come at the expense of
TRANSLATIONAL kinetic energy. The connection between speed of the center
of mass and speed of rotation (the condition of rolling) is broken.
J. Epstein