How much lift do planes produce before rotation?
Check out this plot (taken from wikipedia), of the lift coefficient against angle of attack. During takeoff roll, lift will be increasing due to the speed increasing, however not enough (in general) for the plane to achieve takeoff without rotation.

Once rotation starts, the lift increases dramatically, for (a very rough) example, consider a plane on takeoff roll, then rotating to 15 degrees angle of attack. By looking at the lift/AoA plot, we can see that the lift coefficient increases from roughly 0.55 to 1.7, giving roughly 3 times as much lift as before rotation.