Step 1
Preheat the oven to 425° F. On one large, rimmed sheet pan, combine the onion, squash, and 2 garlic cloves. Toss with 3 tablespoons olive oil and 1 teaspoon salt and spread into one layer. On a second large, rimmed sheet pan, combine the eggplant, bell pepper, remaining garlic, and toss with another 1 teaspoon salt and 5 tablespoons olive oil. Spread into one layer. Roast both trays, placing each on its own rack, for 30-40 minutes, stirring 2 to 3 times or until soft and starting to brown.
Step 2
Add the tomatoes to the eggplant sheet pan and toss. Roast another 15 to 20 minutes or until tomatoes burst.
Step 3
Combine the eggplant mixture with the squash mixture in one sheet pan, add the olives and spread into a single layer.
Step 4
Pat the sole dry, fold the thin ends under and place on top of the vegetables. Sprinkle the fish with the thyme, season with 1 teaspoon salt and 1/2 teaspoon pepper and drizzle with the remaining tablespoon olive oil. Bake until fish is cooked through, about 8-10 minutes. Serve with lemon wedges.