The above is the recipe as it was originally provided.
210 C seems to work OK, at least on our oven.
Ten small Idaho potatoes, and a pair of small-to-medium yellow onions works well. More carrots doesn't hurt, either.
The seasoning here is kindly pale. Parsley, rosemary, and bay leaves work well. It also can help to add water, ¼ to ⅓ of a cup, to the pan to help steam everything and let the bay leaves do their magic.
Adapted from Kelly Roenicke's recipe on theprettybee.com/roasted-carrots-potatoes-and-onions