Preheat the oven to 400°F. Line a large, rimmed baking sheet with high-heat-resistant parchment paper.
Place the asparagus on the baking sheet in a single layer. After it's trimmed, you should be able to fit two rows of it into the pan.
Drizzle the asparagus with the olive oil, then toss with your hands to coat. Sprinkle with kosher salt, black pepper, garlic powder, and half the parmesan.
Bake until the asparagus is tender-crisp, for about 15 minutes.
Sprinkle the asparagus with the remaining parmesan and serve.
Video
Notes
I use garlic powder in this recipe because its fine granules coat the spears uniformly. If you prefer fresh minced garlic, that works too.
Medium-sized asparagus spears like the ones shown in the video above are best. If all you can get is thin or thick spears, you can use them in this recipe, adjusting the roasting time. Very thin spears will need no more than 10 minutes in the oven. If using thick ones, check them after the first 15 minutes and see if their thickest parts are fork-tender. If not, keep roasting them for 2-3 more minutes.
You should always trim asparagus ends, but if using thick spears, it's especially important to trim them; they tend to be woody and fibrous.
Dry the asparagus well with a clean kitchen towel or paper towel after washing so it bakes rather than steams in the oven.
You can keep the leftovers in the fridge in an airtight container for 3-4 days. You can chop them and add them cold to a salad or gently reheat them in the microwave at 50% power.