The stability ball ab rollout is a great exercise if you don't have an ab wheel available. But it's also a good choice if the standard ab rollout is too difficult for you right now.
It's essentially a partial rollout since your body isn't going down as far. You can start with a large ball, move to a smaller one as your core gets stronger, and finally do the ab wheel with the full range of motion.
It's a fact: the exercises that make you hate life the most also tend to deliver the best results. If you're in serious need of a hamstring overhaul, then this article is a great (although painful) place to start.