I am new to the ROC analysis, but I need to learn for my biomakers analysis. I am trying to see if some biomarkers are capable of discriminating my ppopulation between two groups. For this, I am using the following commands:

1º logistic depvar predvar
2º lroc
3º lstat

I guess my data are too unbalanced cause I'm getting very high specificity for my model (some are 100%), but very low sensibility (even 0%). I saw that I need to do resampling or bootstraping, but I have no idea how to do it. Could somebody help me somehow?