Roasted Vegetable Sandwiches

Name: Roasted Vegetable Sandwiches
Ingredients: 1 small eggplant, thinly sliced into rounds; 1 zucchini, thinly sliced; 1 yellow summer squash, thinly sliced; 1 red bell pepper, cored, seeded and thinly sliced; 2 teaspoons extra-virgin olive oil; 2 cloves garlic, finely chopped; Salt & freshly ground pepper, to taste; 1/4 cup nonfat sour cream, or nonfat plain yogurt; 2 tablespoons reduced-fat mayonnaise; 1 tablespoon chopped fresh basil; 1 teaspoon lemon juice; 1 16-inch-long French baguette, split lengthwise and cut into 4 sections; 1 bunch watercress, washed, large stems removed (about 2 cups)