My experiment above (riding with the bike tilted) demonstrated to my satisfaction that gyroscopic effect is minimal. The main reason a cyclist is able to balance is by sensing slight shifts in gravitational pull and steering accordingly. if you are starting to tip left, you steer left. As you point out yourself in a later post, even on rollers you have that ability to move the bike from side to side, to keep it below your centre of gravity, much like a person balancing a broom on their finger keeps moving it from side to side. It's easier to balance at higher speeds because you need to make only minor steering adjustments to quickly correct any tilt, and because the geometry of the fork makes the bike want to turn the way it is tilted and thus correct any tilt, and NOT because of the gyroscope effect.
Robert