Your code is really clean. It almost respect pep-8. Try to install flake8 and check your code:

flake8 main.py

I am a big fan of docstring that will make your functions shine more ! My favorite format is the google one, but numpy is also a good choice.

For example your die function in functions.py would look like:

def die(count: int, size: int = 6):
    """ Generate dice rolls

    Args:
        count: number of rolls
        size: number of faces

    Returns:
        list of rolls
    """
    dice = [randint(1, size) for _ in range(count)]
    return dice

Finally the last bit of advice would be about organization of your files. We usually put the functions/classes in a specific folder. You could for example move armor.py, races.py, weapons.py classes.py functions.py into a src/ folder.

Let me get it straight to you, your code is overall clean, well organized and documented, the advises will only make your code looks "more professional". If you want to be fancy you could also implement few pytest then set up Travis and codecov, you'll be able to brag with badges !

Congratulations for self-teaching yourself python !