Preheat oven to 400℉. On a baking sheet, toss green beans with oil and season with salt and pepper. Roast for 10-12 minutes until slightly brown and crisp-tender.
Meanwhile, in a small skillet, cook the pancetta until brown and crisp, 5-7 minutes. Transfer the pancetta to a paper towel-lined plate. Wipe the pan clean with a paper towel.
Over medium-low heat, melt the butter and whisk in the juice of ½ an orange until the sauce comes together. Season with salt.
Transfer the roasted green beans to a serving platter and pour the sauce over the top. Garnish with the orange zest and pancetta.
Notes
Roasting green beans:
If using thin haricots verts, reduce the roast time by a few minutes.
Buy fresh beans that are firm and have a vibrant color.