Displaying many ROC-curves

I did a classification using Classify. I sampled 20 times. To calculate the mean accuracy, etc., is easy. But is there also a way to overlay the calculated ROC curves? If one uses Overlay the output is not really pretty

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I think it would be nice the overlay the graphs with decreasing opacity, so that one could see the different curves. I tried with Opacity but could not get it to work.