Depends on your price range. Trigger point ones are a little expensive but really good, and there's a fair variety in them. They're more solid as well, the cheap foam rollers can 'wear down', but it's a bit hard to describe.
Anyone that gets tight calfs, I invested in a foam roller and 'roll out' three times a day, every day, and my calfs certainly are much looser and tighten up a lot less running.