Open your right hand with the palm facing up, you thumb at a right angle to the fingers. You can easily visualise this with your hands.
However, if initially the roll angle was non-zero, the roll angle will be affected by a pitch-up manoeuvre. If the aircraft pitches up ( $q$ becomes positive for a while), the roll angle will not change. Initially on the runway the roll angle of the aircraft is 0 degrees. This describes almost every possible attitude uniquely, unless the pitch angle is +/- 90 degrees. The rotations are applied in backwards order, first yaw ( $\psi$), then pitch ( $\theta$) and finally roll ( $\phi$). The angles $\phi, \theta, \psi$ describe the attitude with respect to this initial positions. Initially when all angles are 0, the aircraft is wings level, nose pointing at the horizon and heading north. Yaw rate is denoted $r$, yaw angle is denoted $\psi$ Z-axis is the vertical axis pointing down.Pitch rate is denoted $q$, pitch angle is denoted $\theta$ Rotation about the Y-axis is called pitch. Y-axis is the lateral axis pointing out the right wing.Roll rate is denoted $p$, roll angle is denoted $\phi$ Rotation about the x-axis is called roll. X-axis is the longitudinal axis pointing out the nose of the aircraft.Roll angle, pitch angle and yaw angle together describe the attitude of an aircraft. Roll, pitch and yaw are rotations about the principle body axis of the aircraft.