For a streamlined, stress-free meal, slide this shrimp scampi supper into the oven. Preheating the baking sheet gives the sliced potatoes a headstart to crispness, and the broiler steps in at the last minute to cook the garlicky shrimp.
Preheat oven to 475°F, with a rimmed baking sheet on center rack and another rack in top position. Toss potatoes with 3 tablespoons oil; season with salt and pepper. Spread in a single layer on sheet and roast on center rack, flipping once, until beginning to brown, about 15 minutes.
Meanwhile, toss asparagus with 1 tablespoon oil, and toss shrimp with remaining 1 tablespoon oil, oregano, and garlic. Season both with salt and pepper.
Remove sheet from oven; flip potatoes and push to one side, then add asparagus to other. Roast until potatoes are just tender, 6 to 7 minutes. Switch oven to broil; add shrimp and lemon rounds on top of asparagus and potatoes.
Broil on top rack until shrimp are opaque and browned in places, and asparagus and potatoes are cooked through, about 3 minutes more. Serve.