Preheat oven to 450 degrees F (230 degrees C). Line a rimmed baking sheet with aluminum foil.
Put eggplant cubes in a colander set over a bowl. Sprinkle salt liberally over the eggplant cubes; let sit to drain for 30 minutes.
Toss tomatoes, zucchini, onion, and garlic together in a bowl. Drizzle olive oil over the mixture and toss to coat; season with salt and pepper.
Rinse eggplant to remove salt and pat dry with paper towel; add to the tomato mixture and stir. Add olive oil as necessary to assure the eggplant cubes are coated. Spread the vegetable mixture onto the prepared baking sheet.
Roast in preheated oven until the vegetables are tender, about 30 minutes.
