A cylinder rolls up an inclined plane, reaches some hight, and thenrolls down (without slipping through these motions). The directions offrictional force acting on the cylinder are

The direction of the frictional force will be up the inclined plane in both the motions.The friction acts opposite to the relative motion of the point of contact on ground.In both the cases the force acting on the point of cylinder in contact with the plane is mgsin(theta).As there is pure rolling the velocity and acceleration of the point of contact must be zero. SO friction acts upwards along the inclined plane.