The ROC (Receiver Operating Chracteristic) curve makes a comparison between the GAR (1-FRR) and the FAR variations. The values range from 0 to 1.
In order to have a rough value of the overall accuracy of the system, we can compute the Area Under the ROC Curve (AUC). Higher this are, higher the performances of the system. This because the curve will be most on the upper part, and so it will have a ratio between Genuine Acceptance and False Acceptance closer to 1.
Another curve is the DET (Detection error Trade-off), that describes the ration between FRR and FAR. Lower the curve is, the better.