If you get a JP group say:

<--- 石 me ok!

This means you will get stones. Dont stray to far from healer stay within medica range but far enough that you can get to the next rock quickly. You cant avoid roar just need to mitigate with succor or be in range for medica to clean up. Ultimately its best if healer gets rocks.

Some tend to tank in center and range players (healer blm brd smn etc etc) satellite around the room dealing with stones and maintaining a good range from one another for heals etc. Another way is to tank boss where adds come in and just use the stones in that general area as you can kill this boss by the time you use 2-3 stones so there is enough in that general spot that its pretty safe.