Here's a link to the Test the Dice Roller Thread where you can post rolls until you're comfortable.
The basic roller works like this:
{roll}1d20+4{/roll} but you need to replace the { and } with [ and ]
So, replacing them gets me: [roll0]
You can also add a tag by doing {roll=Blah}1d20+4{/roll}, which when replacing gets me:
[roll1]
Personally, I don't use the roll titles because they have a tendency to screw up.
One final thing, you can't add multiple dice into the same roll tag. So, if you're using a battlemaster maneuver that adds damage dice to the roll, you need to roll them separately.
{roll}1d10+5{/roll} + {roll}1d8{/roll} gets you [roll2] + [roll3], which you then need to go back and provide the addition (13 in this case). If the extra damage die matches the weapon damage die (i.e. they're both d8s, you can technically roll them as one total, but I'd just get into the good habit of rolling them separately.