Preheat your oven to 400 degrees Fahrenheit and line a large rimmed baking sheet with parchment paper.
In a large mixing bowl, combine the cubed chicken breast, diced eggplant, zucchini, red bell pepper, and red onion.
Drizzle the olive oil over the mixture and sprinkle with dried thyme, sea salt, and black pepper, tossing well to ensure every piece is evenly coated.
Spread the vegetable and chicken mixture in a single layer on the prepared baking sheet, ensuring they are not overcrowded to allow for proper browning.
Roast in the center of the oven for 20 minutes until the chicken is mostly cooked through and the vegetables begin to soften and caramelize.
Remove the pan from the oven and carefully stir in the tomato puree and minced garlic, spreading the sauce evenly across the roasted ingredients.
Return the pan to the oven for an additional 10 minutes until the sauce is bubbling and the vegetables are perfectly tender.
Garnish the ratatouille with freshly chopped basil before serving warm.