The Rate of Change Indicator is a simple yet effective momentum oscillator. It measures the relative percentage change of the prices from one period to the next. The calculation looks at the current price and compares it to the price of n periods ago.
As long as the ROC is above 0, the uptrend is intact. As long as the ROC is below 0, the downtrend is intact. Divergences between the indicator and the price development can hint to a trend change.