1Heat oven to 450°F. In 8-inch nonstick skillet, cook pancetta over medium-high heat until crisp. Drain on paper towels; set aside. Reserve drippings.
2In 18x13-inch half-sheet pan, toss green beans, onion, oil, salt, pepper and reserved drippings.
3Roast uncovered 15 to 20 minutes, stirring twice, or until beans are tender. Sprinkle with pancetta.