"For cross-validated data, you must specify Labels, Scores, and Weights as cell arrays with the same number of elements. rocmetrics treats an element in the cell arrays as data from one cross-validation fold and computes pointwise confidence intervals for the performance metrics. The length of Labels{i} and the number of rows in Scores{i} must be equal."
You need to supply the fold weights.
Alternatively, you could loop over the folds to see ROC metrics on each fold, or decide prior to calling rocmetrics how you want to combine the folds into a single prediction.
