In a medium bowl, mix the vinegar, olive oil, rosemary, and a bit each of salt and pepper. Add the pepper strips, turning to coat, and set aside to marinate for at least 30 minutes. This also can be done up to 3 days ahead.
When ready to grill, return the grill to high heat.
Set the mushrooms and zucchini in a large bowl. Pour the marinade off the peppers and onto the zucchini and mushrooms, tossing them lightly to coat well.
Grill the mushrooms, gill side up, for 8 to 10 minutes, then flip and grill for another minute, or until completely tender. Grill the zucchini slices for 3 minutes per side.
Split the rolls in half. Brush the cut sides lightly with oil. Place cut side down on grill for 2 to 3 minutes, or until golden brown.
Meanwhile, in a small bowl, mix together the garlic and mayonnaise until smooth. When the rolls are toasted, assemble the sandwiches by spreading both sides with garlic mayonnaise, then layering a mushroom, zucchini, peppers, basil leaves, cheese and prosciutto. Season with salt and pepper, if desired.
Nutrition information per serving (without the optional prosciutto): 610 calories; 290 calories from fat (48 percent of total calories); 32 g fat (8 g saturated, 0 g trans fats); 30 mg cholesterol; 53 g carbohydrate; 5 g fiber; 11 g sugar; 26 g protein; 1220 mg sodium.
This is one of those pantry items that make almost any recipe better. Substitute roasted garlic for raw cloves when you want a mellower, smoky flavor. And if you are roasting one head, you might as well go ahead and make a few extra; they keep in the refrigerator for at least a week. Wrap each head in its own sheet of foil for easy grilling and storage.
Start to finish: 40 minutes (mostly inactive)
Makes 1 head
1 head garlic
2 teaspoons olive oil
Heat a grill to medium, with one side prepped for indirect heat (for charcoal grills, bank the coals to one side; for gas grills, turn off one burner).