The easiest way to do this is by keyframing the animation. Set a few keys, mess with the tangents a bit, and you'll get the result you need.
Alternatively, if you're looking for a generalized velocity/acceleration solution, consider using particle or solid body dynamics. You can apply forces or accelerations and rely on the dynamics solver to figure out the resulting motion.
Finally, you can try using a mathematical expression for the rotation. This is my least favorite approach because it requires figuring out how you want the velocity to change and then essentially analytically integrating it, which if you don't recall your calculus very well is going to be a trouble-filled, trial-and-error endeavor.