Preheat the oven to 450 degrees Fahrenheit. Line a baking sheet with parchment paper.
Chop the broccoli into medium-sized florets, leaving a good amount of the stem for a nice shape. Chop the cauliflower into florets. Mix both with the olive oil, garlic powder, and kosher salt.
Roast for 20 to 25 minutes, until tender and slightly browned (no need to stir!). Roast a few more minutes if not yet browned. Enjoy immediately.