Wash and dry all produce. Adjust rack to upper position and preheat oven to 450 degrees. Halve, peel, and finely chop shallot. Strip and finely chop enough rosemary leaves from stems to give you 2 tsp. Cut potatoes into ½-inch cubes.
Toss potatoes on a baking sheet with a drizzle of olive oil, 1 tsp chopped rosemary, and a pinch of salt and pepper. Roast in oven until tender and crisped, 20-25 minutes, tossing halfway through.
Meanwhile, heat a drizzle of olive oil in a large pan over medium heat. Season pork with salt and pepper. Add pork to pan and sear, turning occasionally, until browned all over, 4-8 minutes. Transfer to another baking sheet.
Toss green beans with a drizzle of olive oil and a pinch of salt and pepper on same sheet with pork. Roast both in oven until pork reaches desired doneness and green beans are tender, 10-12 minutes. Let pork rest a few minutes after removing from oven, then cut into thin slices.