How can validate hub genes or significant factors using area under the ROC curve (AUC)?

Question

[wyt1995]

In previous research, we can identify hub genes and significant factors for specific diseases. After, to ascertain whether these identified results are significant, a validation process is needed. During this process, we can use AUC results to determine significance statistically. While many papers showed such results, [1], [2], [3], and [4] are examples.

I do not fully understand how they obtain those plots. I would appreciate it if you could explain the process.