Preheat oven to 400 degrees F. In a small bowl, combine parsley, garlic, rosemary, thyme, salt, and pepper. Set aside 1 tablespoon of the herb mixture.
Place turkey breast portion, bone side down, on a roasting rack in a foil-lined shallow roasting pan. Lightly coat with nonstick cooking spray. Sprinkle the remaining herb mixture evenly over turkey breast portion; rub in with your fingers. Roast, uncovered, for 20 minutes.
Meanwhile, in a large bowl, combine potatoes, carrots, and pearl onions; add the reserved 1 tablespoon herb mixture and the olive oil and toss until vegetables are coated. Arrange vegetables around turkey in roasting pan.
Reduce oven temperature to 350 degrees F. Roast for 1-1/4 to 1-1/2 hours more or until juices run clear, turkey is no longer pink (170 degrees F), and vegetables are tender, stirring vegetables once.
Transfer turkey to cutting board; tent with foil and let stand for 10 minutes before carving. Trim meat from bone. Serve turkey with the vegetables (see Tip).
Storage: Place any leftover cooked turkey and vegetables in an airtight container. Cover and store in the refrigerator for up to 2 days or freeze for up to 3 months.