Slå Tärning (Syntaxfel)

import random

print("Roll dice")

def roll (sides=12)
num_rolled = random.randomint (1,sides)
    return num_rolled

def main()
    sides = 12
        rolling = true

            while rolling:
                roll_again = input ("Please press the button in order to roll the dice. TAB=Roll Q=Quit. ")
                if roll_again.lower () != "q":
                    num_rolled = roll (sides)
                    print ("You rolled a", num_rolled)
                else:
                    rolling = false

    print("Thanks for playing")

Felmeddelande:

  File "e:\Program\Python project files\Project 2", line 5 
    def roll (sides=12) 
                                 ^ 
SyntaxError: invalid syntax

Varför är det fel??