The BB code for dice goes around what you want to roll like: 3d8
Maximum allowed number of dice is 20 and you can add modifiers like 3d6+5
How a dice roll looks in your post can be modified in the user setting.
(User Control Panel->board preferencess->dice game)
Default is text, but other styles look more fancy
Also i the text or pictures do have a tool tip when you hover with the mouse over it, so you can distinguish between real rolls and (cheap) cheat attempts