Step 1: Preheat your oven to 400°F (200°C). Line a large rimmed baking sheet with parchment paper for easy cleanup. This prevents sticking and makes tossing the pan much simpler after dinner.
Step 2: Slice your chosen pre-cooked sausage into ½-inch thick rounds. Halve or quarter your potatoes into uniform 1-inch pieces; this ensures they cook evenly and get delightfully crispy. Trim the ends of your fresh green beans. In a large bowl, combine the sliced sausage, cut potatoes, and trimmed green beans.
Step 3: Drizzle the ingredients generously with olive oil. Sprinkle with garlic powder, onion powder, smoked paprika, salt, and black pepper. Toss everything together until each piece is well coated. Make sure the seasonings are evenly distributed for the best flavor in every bite.
Step 4: Spread the mixture onto your prepared sheet pan in a single, even layer. It's crucial not to overcrowd the pan; this allows the ingredients to roast and caramelize rather than steam. Place the pan in the preheated oven and roast for 30-40 minutes, stirring everything halfway through the cooking time. The potatoes should be fork-tender and golden-brown, the green beans tender-crisp with a slight char, and the sausage beautifully browned.