Heat a grill to high (450° to 550°). In a blender, whirl 1/3 cup oil with the rosemary, parsley, salt, and pepper until smooth; set dressing aside.
Brush peach halves and baguette slices with remaining oil. Grill until marks appear, about 2 minutes, turning as needed.
Lay prosciutto on plates. Toss arugula in a medium bowl with half the reserved dressing and arrange over prosciutto. Sprinkle with cheese and drizzle with remaining dressing and the sherry. Set peaches and toasted bread around salads.
*Available from avalanchecheese.com