This post appeared on my old blog, but it seems appropriate timing, given the 50 mile race this weekend.
Using a foam roller is one of the best things you can do for injury prevention, especially athletes. I became a fan when I increased my running volume to do a 100 mile race, but then really became a fan when I realized I didn't have to work as hard when my clients rolled between massages, And while I love working hard for my clients, I love longevity even more. By foam rolling between sessions, I can be more effective during each treatment session and clients see better results. Rolling can also be an effective tool in repatterning movement patterns (but that's a whole other post).
You might feel tightness in your hamstrings and hips, but runners in particular benefit from rolling the quads and hip flexors. The front of the thigh and hip flexors often compensate for the glutes (especially if your glutes are weak), resulting in shortened, tight muscles. Working on hip extension is essential for this, both in your technique while running (work with a coach on this, or at least check out this book) and opening the front of the hips when you aren't running. Enter: the foam roll. It won't be the most pleasant when you start (read: painful), but you can adjust how much of your body weight goes onto the roller, and after even a few minutes daily, it will begin to feel much better. Your legs will thank you.