In what way do you want it to work? I have a couple of simple modifications, shown in the image below:
First off, when you get the input from the user, set it to a singular letter case (upper or lower) so that you can make comparisons more easily (without the modification on line 13 above, a user typing "Yes" would have the program exit).
Second, you had this after the while loop: if roll_again != "yes" or "y": However, that is redundant since the while loop already checks that at the beginning of the loop every time. When it exits the loop, this condition will always be true.