Pasta with Oven Roasted Vegetables and Avocado

3 medium zucchini, cut in half lengthwise and sliced

1 medium red onion, sliced into crescents

1 leek (white part only) thinly sliced, rings separated

1 medium red bell pepper, cut into 1-inch pieces

1 medium yellow bell pepper, cut into 1-inch pieces

1 Chinese eggplant, cut in half lengthwise and sliced

3 tablespoons balsamic vinegar, divided

1 tablespoon olive oil

5 medium cloves garlic, finely chopped

½ teaspoon salt

1 teaspoon ground black pepper

8 ounces whole grain penne pasta, cooked according to package directions

½ cup salt-reduced, fat free vegetable broth

1 tablespoon chopped fresh basil leaves

1 ripe avocado, seeded, peeled, and cut into 16 slices

Fresh basil leaves, for garnish