No, that's Rate of Return, not Return on Investment. Rate of Return measures a CASH FLOW, while Return on Investment measures the total return.
Rate of return would be used on for example an investment where you invest 1 BTC, and then get 0.2 BTC every month. That would be a rate of return of 20%.http://en.wikipedia.org/wiki/Return_on_investment
EDIT: Actually, on closer inspection, it seems that there are simply multiple ways of calculating ROI, and this is just the way I've been taught. I think mine makes more sense, though, since it tells you how much of your investment you get back, and if that's above 100%, then you've made a profit. If it's below 100%, it's a loss. But eh, seems like both are correct.