How can I visualizing multiple ROC curves?

Suppose that I have some pairs of parameters:

(x1, y1), (x1, y2), ..., (x1, yb)

(x2, y1), (x2, y2), ..., (x2, yb)

...

(xa, y1), (xa, y2), ..., (xa, yb)

For each pair of parameters, I computed a ROC curve (TMR and FNMR).

The question is: How to visuallize the ROC curves on the same graph?

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Currently, I draw a different 2D graphs (for different x_i), each graph contains b ROC curves.

[huynhlv]

I'm thinking of using a 3D graph/contour with color, but I have not able to imagine how it will be.