Preheat your oven to 425 degrees Fahrenheit. While the oven is heating, wash your green beans thoroughly and pat them completely dry with a kitchen towel. It is important that the beans are dry so they roast instead of steam. Line a large baking sheet with parchment paper or a silicone mat for easy cleanup.
Place the trimmed green beans in a large mixing bowl. Drizzle with the olive oil and add the minced garlic, salt, pepper, and onion powder. Toss everything together with your hands or tongs until every bean is evenly coated in the oil and seasonings.
Sprinkle the grated Parmesan cheese and panko breadcrumbs over the seasoned green beans. Toss gently once more so the cheese and crumbs adhere to the oily surface of the beans. Spread them out in a single layer on your prepared baking sheet, making sure they are not overcrowded.
Slide the baking sheet into the center rack of the oven. Roast for 12 to 15 minutes, or until the green beans are tender and the Parmesan crust is golden brown and crispy. You can toss them halfway through the cooking time if you want even browning, though it is not strictly necessary.
