As FHHuber explained, Rudder input provides roll control in any airplane with much dihedral effect. Regardless which control surface is used, a proper turn always involves banking the airplane. Use of ailerons to bank the airplane is the right way to make a turn whenever it is in flight, even when landing. For small corrections use a slight bank. If an aircraft has ailerons, the only need for rudder control is in aerobatic flight involving sideslips and for taxi. (For the purest, "slight" use of rudder when ailerons are applied to counteract adverse yaw is theoretically required, but since there is no way to feel the yaw from the ground, most simply ignore it).

Yes, rudder can be used in an emergency to fly the airplane. Many airplanes are designed to fly with rudder as the only roll control and they can do a remarkable range of aerobatic maneuvers even without ailerons. But if ailerons are installed, controling the plane with rudder only dosen't make much sense.