Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Cut the chicken breast, eggplant, zucchini, and red bell pepper into uniform 1-inch cubes.
Place the chicken and vegetables on the baking sheet and drizzle with olive oil.
Sprinkle with sea salt, black pepper, and dried oregano, then toss thoroughly to coat.
Spread the mixture in a single layer and roast for 20 to 25 minutes until the chicken is cooked through and vegetables are tender.
While roasting, mince the garlic and add it to a small saucepan with the tomato puree over medium-low heat.
Simmer the sauce for 5 minutes to meld the flavors.
Remove the sheet pan from the oven and transfer the roasted chicken and vegetables into a large bowl.
Pour the warm tomato sauce over the mixture and toss gently before serving.