Preheat oven to 325 degree F. In a large skillet brown meat on all sides in hot oil. Transfer meat to a shallow roasting pan. Sprinkle meat with garlic, rosemary, thyme, salt, and pepper. Place parsnips and pears around meat. Pour wine over all. Loosely cover with foil; bake for 2 to 2-1/2 hours or until an instant-read thermometer inserted in center of meat registers 160 degree F.
Transfer meat to serving platter, reserving cooking liquid; use a slotted spoon to transfer parsnips and/or carrots and pears to serving platter. Cover with foil while preparing sauce.
For sauce, measure 1-1/2 cups cooking liquid. In a medium saucepan stir together cornstarch and water; add cooking liquid. Cook and stir over medium heat until thickened and bubbly; cook and stir for 2 minutes more. Season with additional salt and pepper. Remove string from roast and slice meat. Serve sauce with meat and vegetables. Makes 10 to 12 servings.