Tony - the mods have helpfully added the posts from a previous thread at the beginning of this one which may help (after the initial confusion of 'that wasn't there earlier').
However, flapback and inflow roll are both examples of flapping to equality - which is exactly what it says on the tin - there is a difference in lift (whether through speed, induced flow or AoA) between one side of the disc and the other which causes the blades to flap. Aerodynamic damping (as a blade flaps up it's induced flow starts to increase so the AoA reduces and the extra lift is lost) stops the blade continuing to rise or fall. The blades inertia means that the effect of the lift change increases and decreases gradually.