I used to roll my ankles at least once a month and actually rolled one so hard that it broke the end of my 5th metatarsal off!
For me, the cure was strengthening the muscles and connective tissue around the joint. I did this by changing my running technique and running shoes. Now I am a fore-foot striker and I run in Vibram Five Fingers. My calves, ankles, and foot muscles had a lot of catching up to do, and were sore for a while.
It's much harder to roll your foot on it's side when you land on your forefoot. It's much wider and flatter than your heel. think of it like this:
\___/ vs \_/
Which one would tip over easier?
I'm happy to say that I haven't rolled an ankle in over 4 months and they don't pop when I walk anymore.
Let me know if you'd like a more detailed explanation of how I overcame this problem.