My first try with python

[nilamo]

Oh hey, D&D!  I also once wrote a roller: http://dnd.nilamo.com/
It's different from what you're working on, though, as mine was made for character generation (roll 4d6, 6 times for a row, for 6 rows to make a grid, reroll all 1s, and add the three highest numbers to get a stat, then choose any row/column for your base stats).
 

I thought about that, but I don't really know how to do that

Something like:

>>> response = input("Roll: ")
Roll: 2d20
>>> number_of_dice, type_of_dice = map(int, response.lower().split("d"))
>>> number_of_dice
2
>>> type_of_dice
20