Acceleration of the rolling sphere,
a=gsinθ/((1+k²/R²))
Velocity of the sphere at the bottom of the inclined plane,
v=√(2gh/((1+k²/R²)))
The sphere will take a longer time to roll down one plane than the other. It will take a larger time in case if the plane with smaller inclination because the acceleration is proportional to sinθ.