Preheat oven to 425 degrees F. In a 15x10x1-inch baking pan toss onions with 2 tablespoons of the oil, 1/2 teaspoon of the salt, and 1/4 teaspoon of the black pepper. In another 15x10x1-inch baking pan toss eggplant with another 2 tablespoons of the oil and the remaining 1/2 teaspoon salt. Roast onions and eggplant about 40 minutes or until softened and beginning to brown, stirring onions and eggplant and rearranging pans in the oven halfway through roasting time. Let cool for 10 minutes.
In a large bowl combine onions and eggplant. Stir in tomatoes, raisins, olives, capers, vinegar, honey, garlic, and the remaining 2 tablespoons oil. Cover bowl with plastic wrap. Chill for at least 4 or up to 24 hours.
Let stand at room temperature for 30 minutes before serving. Stir in parsley and marjoram. If desired, serve with rustic crackers and/or bread slices.