Prepare/set your grill to medium-high heat.

Begin by preparing the garlic for roasting. Peel off the outer papery covering of the head of garlic. Using a sharp knife, slice off 1/4-inch of the top of the bulb, so that the inside of each clove is exposed. Place the head on a square of aluminum foil. Drizzle 1 tsp. olive oil over the top of the cloves, and then use your fingers to spread it around well. Then fold up the foil over the top of the clove, so that it is fully enclosed. Set the foil package directly on top of the grill grates and cook, covered, for about 20 minutes (or until garlic cloves are soft and lightly golden).

Meanwhile, in a large bowl, combine tomatoes, onion, zucchini, squash, and mushrooms with 2 Tbsp. of olive oil and a generous amount of freshly-ground salt and pepper. Then toss until vegetables are evenly coated. Transfer vegetables to a grill pan, and set on the grill grates (next to the foil-wrapped garlic). Grill, stirring every 2-3 minutes, until vegetables are tender and lightly charred. Remove garlic and vegetables from grill when cooked.

While vegetables are cooking, prepare the dressing. In a small bowl, whisk together the remaining 2 Tbsp. of olive oil, balsamic vinegar, all of the roasted garlic cloves (you can use your fingers to squeeze them out of the clove), and the chopped fresh herbs (optional) until combined. Add extra salt and pepper to taste.

Transfer vegetables to a serving platter or bowl, and drizzle with the prepared dressing. Serve immediately. (Or these are also delicious served cold or at room temperature!)