Bloated? That's when you remove comments and formatting and jam it all into the same number of lines. Make NumDice optional for additional triggering.

int DnDRoll(const int& NumSides, const int& NumDice) {
    int returnRoll = 0;
    For (int i = 1; i <= NumDice; ++i){returnRoll += rand() % NumSides + 1;}
    return returnRoll;
}

This is literally any programming question.

Nobody does that, why do you want to do it?

YOU STUPID ASSHOLES, THE FACT NOBODY ELSE DOES IT IS THE VERY REASON I NEED TO WRITE A PROGRAM TO DO IT.