ROC-AUC loss for GRU Model: Cannot use tflearn's loss in keras
This worked for me when I changed the declaration of the function:

def roc_auc_score(y_true, y_pred)


instead:

def roc_auc_score(y_pred, y_true)


I defined it wrong and it worked, when I fixed it I got the same error as you do. I don't really understand your code logic, but you can if this works for you.