I just discovered that Siri can roll a d20. (Or a d4, d6, d8, d10, d20, or d100.)
— James Wyatt (@aquelajames) April 9, 2015
"Roll a d20" or "roll a 20-sided die" both work. Doesn't do multiple dice or modifiers. But "roll the dice" does 2d6.
— James Wyatt (@aquelajames) April 9, 2015