The main ingredients of ratatouille are tomatoes, onions, peppers, zucchini & this veggie that's bigger than those
The Larousse Gastronomique claims "according to the 
purists, the different vegetables should be cooked separately, then combined and
... [DOC] [TLE] Multi-Vegetable Recipes | Open Hands Farm [PAR] Mar 2, 2015 ... Roasted Maple-Bourbon Carrots and Parsnips Ingredients 3 lb.