Quaternions

You're looking for euler angles World elements have a convenient method to set the rotation by providing an x, y and z rotation (pitch, yaw, roll): worldElement.setRotation(pitch, yaw, roll)
Remember that you have to provide your rotation in radians, not degree. You can use Utils.MathUtils.degreeToRadians(float) to convert your degree value (0-360) to radians.

Alternatively, when working with quaternions, you can call quaternion.fromAngles(pitch, yaw, roll) to build the quaternion from euler angles (again, radians). To convert a quaternion into euler angles, you can call quaternion.toAngles()