There are several parts to the Canadian/Indian stroke, and it might help to consider them separately.
During the forward stroke phase, you can do a normal "J" stroke or you can do what's called a pitch stroke. This involves turning the paddle a bit beyond square so it exerts a little pushaway force during the stroke in addition to forward propulsion. It's like starting the "J" stroke early, and it has the same effect, to move the stern away from the paddle.
During the recovery phase, the blade stays in the water and is sliced forward with just a little bit of a drawing action. This is done by opening the blade slightly as it's moved forward through the water. Its effect on the boat is the same as the "J", both of which counteract the natural deflection of the forward stroke.
The palm roll occurs in the brief transition between these two phases, at the end of the forward-stroke phase and before the recovery phase. With the paddle in the final "J" position, you grip the shaft a little more firmly, open your grip hand a bit and cock the wrist (turn the thumb toward you a bit), at the same time as using your shaft hand to rotate the paddle just a little more. (The hands turn in opposite directions.) Keep the paddle grip against your palm during this movement. When the grip seats itself again in the palm, loosen your shaft hand and re-grip the paddle with your grip-hand thumb facing backwards toward the stern. Then slice the paddle forward for the in-water recovery.
I hope this helps!