1. To prepare oven-roasted potatoes, heat oven to 450 degree F. Combine potatoes with 2 tablespoons olive oil, 2 tablespoons rosemary, 1 teaspoon pepper and 1/4 teaspoon salt in a large bowl. Spread potatoes on large cookie sheet and roast, turning occasionally, until the potatoes are nicely browned on all sides, 20 to 25 minutes.
2. Meanwhile, heat grill.
3. Brush both sides of bell peppers, zucchini, yellow squash, eggplant, and red onion with 1/3 cup oil. Grill vegetables in batches 4 to 6 minutes per side, until softened and lightly charred. Transfer to large plate and cool.
4. For the garlic-mustard vinaigrette, combine garlic, mustard, vinegar, Worcestershire, pinch salt, and 1/4 teaspon pepper in small bowl. Gradually whisk in 2 tablespoons oil until mixture has thickened. Stir in 1/2 teaspoon herbs.
5. Coarsely chop eggplant, squash, and onions. Peel and seed bell peppers and slice into thin strips.
6. Place the potatoes, grilled vegetables, and green onion in a large bowl. Toss with half of the vinaigrette. Transfer salad to shallow serving bowl or platter and pour on remaining vinaigrette. Garnish with fresh thyme, if desired. Makes 6 servings.