Adding two roman-numeral inputs
There are definitely a few things you could improve here.  First, you should create a method to convert a Roman numeral to an Arabic numeral and vice-versa:



def roman_to_arabic(number):

    total = 0

    for i in number:
        if i == 'I':
            total += 1 
        elif i == 'V':
            total += 5
        elif i == 'X':
            total += 10
        elif i == 'L':
            total += 50
        elif i == 'C':
            total += 100
    if 'IV' in number:
        total -= 2 
    if 'IX' in number:
        total -= 2 
    if 'XL' in number:
        total -= 20

    return total


Then, you do not need to write this twice, but can call it like this:

total1 = roman_to_arabic(user1)


Another thing you could do to improve the code is use better names.  You have the inputs named as user1 and user2.  They do not represent users, but Roman numerals as strings, maybe roman_numeral1 would be a better name.  total1 also does not represent a total, but an Arabic numeral converted from a Roman numeral: arabic_numeral1.

Finally, you do not support 'D' (500) or 'M' (1000).  If you support these, you should probably add support for "CM" (900) too.  Otherwise, your code looks pretty good to me.