The roll function does not need to return any value (it is not computing anything.) So, it should be type 'void.'
In our program, we will always be rolling 2 standard dice, so the roll function doesn't need to take any parameters. If we wanted to roll a variable number of dice each time, we would want a parameter of type int for the number of dice.
Your roll function should look like this:
void roll() { // your code here... }