Preheat the oven to 400°F.
In a large mixing bowl, combine the zucchini, potatoes, eggplant, bell pepper, onion, and garlic.
Drizzle the olive oil over the vegetables and sprinkle with oregano, thyme, salt, black pepper, and red pepper flakes if using. Toss until the vegetables are well coated.
Spread the vegetable mixture evenly on a large baking sheet.
Roast in the preheated oven for 35-40 minutes, or until the vegetables are tender and slightly caramelized, stirring halfway through for even cooking.
Remove from the oven and drizzle with lemon juice. Toss gently to combine.
Garnish with fresh parsley before serving.