Place oil in a large skillet set over medium heat. Add onion, sweet pepper, eggplant and zucchini; cook until tender, about 5 min. Add pasta sauce, wine, water and sugar. Bring to a simmer; simmer for 5 min. Remove from heat and let cool to room temperature.
Bake tart shells as per package directions; let cool to room temperature.
Remove tarts from foil liners; place on a parchment paper–lined baking sheet. Divide ratatouille mixture among tarts; sprinkle with Parmesan cheese. Bake in a 350°F (180°C) oven for 10 min. or until filling is heated through.