"Pivot" nested list to tibble

I have a tibble that contains all modeling data from cross-validation (CV) for multiple models. Tibble has 5 rows (because of 5 CV splits) and columns that include data from models (for each split separately), predictions, model performance...
I would like to extract the performance column (perf). Obtaining the results goes like this:

cv_splits$perf$`1`$ranger_model

1 denotes split number and ranger model name of the model. This gives me the output:

$metrics
# A tibble: 1 x 3
  .metric .estimator .estimate
  <chr>   <chr>          <dbl>
1 roc_auc binary         0.654

$conf_mat
          Truth
Prediction ok sick
      ok   51    7
      sick  1    0

$roc_auc
# A tibble: 61 x 3
   .threshold specificity sensitivity
        <dbl>       <dbl>       <dbl>
 1   -Inf           0           1    
 2      0.446       0           1    
 3      0.558       0           0.981
 4      0.558       0.143       0.981
 5      0.560       0.143       0.962
 6      0.563       0.143       0.942
 7      0.566       0.143       0.923
 8      0.575       0.286       0.923
 9      0.598       0.286       0.904
10      0.608       0.286       0.885
# … with 51 more rows

How to transform and save this performance results (preferably as tibble) so I can make quick calculations on them such as (plotting ROC curves, plotting AUC,...)?
I was thinking about having long format tibble as result so the columns would be:

split, model, metric (consists of $metrics, $conf_mat, roc_auc), value (tibble of results)

I'm not sure how to obtain that. I'm also open to suggestion for better formatting of the final results.