As you can probably tell if you've replied to any topic, there is an option to roll dice. These dice are used for random events using your profession as well as with the Natrelmon reserve.
First of all, its important to note that you can only roll dice during a REPLY. You cannot roll dice in an ADD TOPIC. If you are posting first in a topic that requires dice, please reply once just for the sake of rolling the dice.
To roll a dice is simple. Uncompact the below tab, set it to one die, and it will roll a number between 1 and 100 when you post. Since you can't roll on an edit, I see it pointless to try to change what your roll was.
The only real rule I have with this? Don't try to cheat, and don't do dice rolls unnecessarily. Oh, and only roll one die at a time for IC purposes.