Preheat the oven to 420°F or 225℃. Line a baking sheet with foil.
Lightly rub the eggplants, bell peppers, tomatoes and onions with olive oil and set them on the prepared baking sheet. Turn the vegetables halfway through cooking. Roast until the skin is blistered and lightly blackened.
Roast the vegetables for about 40 minutes, and the onions will likely take an additional 10 minutes or so depending on their size.
Put the eggplants and red peppers into a plastic bag, seal and let them rest for about 15 minutes. This will loosen the skins. After they are cool enough to handle, carefully peel the skins off the vegetables and remove the stems. Gently scoop out the seeds from within the eggplant and peppers, and tear or cut the flesh into strips. Slice the peeled onions with a knife.
Whisk together the 2 tablespoons extra-virgin olive oil, vinegar, garlic, salt and pepper, and dress the vegetables, lightly tossing to help incorporate the flavors. Taste and adjust seasoning as needed. Arrange the vegetables in a serving dish and top with olives and chopped parsley.
Cover and refrigerate for at least one hour to allow the flavors to marry. Serve cold or at room temperature, with crusty bread.
