With a post, it is possible to roll dice. The exact dice rolls you can make depend on the game system you are using and the details of your character sheet if you are rolling for a particular character.

To keep things fair, the actual dice roll will be made on the server, and the results are posted once you submit your post. Even if you later edit your post, the dice roll will remain the same - if you rolled an incorrect check, ask your storyteller whether you should roll again, or if you can simply add any missing modifiers to the roll manually.

You select your roll at the bottom of your post, just above the Post Reply button. By default, freeform rolls are enabled. If you have a character sheet, other rolls will also become available once you select your character as a mask. Those rolls based on your character sheet and you don't have to manually add the bonuses from your sheet - they are incorporated into the roll automatically.

You can make multiple roles in your post if you want to. To do so, simply add another dice roll once you finish with the first. Likewise, you can remove dice rolls before you submit your post in case you made an error, though it is not possible to remove eroneous dicerolls once the die has been cast.