Preheat your oven to 425°F. Line a large, rimmed baking sheet with foil.
Add the green beans to the pan and toss them with olive oil, kosher salt, black pepper, and garlic powder. I use my hands to ensure the beans are well coated.
Spread the coated beans in a single layer on the baking sheet.
Roast them until tender and browned in spots, about 15 minutes. Serve immediately.
Video
Notes
As with most vegetable recipes, I urge you to avoid overcooking green beans. You want them to be al dente - just like pasta. When done, they should still have a "bite" and a bit of crunch - you don't want them soft and mushy.
I prefer garlic powder to fresh minced garlic in this recipe because it's easier to evenly distribute. But if you use fresh minced garlic, that's fine, too.
You can keep the leftovers in the fridge, in an airtight container, for 3-4 days. I like to eat them cold, like antipasti. You can also gently reheat them in the microwave, covered, at 50% power.