ROI Calculation

ROI Calculation Is my understanding of how to figure ROI correct? If you have a 100-unit bankroll, are betting 1 unit per bet, and make 1,000 bets in a year, then with a +75-unit win at years end, your ROI would 7.5%. The 75-unit win divided by the total amount bet of 1,000 units. As usual, I've seen it explained differently from one source to another, but think I have it figured out(albeit simplistically at this point).
That's all there is to it. Amount won/Amount Risked.
Thanks. I thought is was pretty straight forward.