Preheat oven to 425°F. Line a baking sheet with parchment paper. (Alternate method: For a shortcut instead of roasting, steam the broccoli instead! Use Best Steamed Broccoli or Instant Pot Broccoli, then go to Step 3.)
Chop the broccoli into medium-sized florets, leaving a good amount of the stem for a nice shape (see the photo). Mix the broccoli florets with 2 tablespoons olive oil and the kosher salt. Roast for 20 to 25 minutes, until tender and slightly browned (no need to stir!).
When the broccoli is done, remove the pan from the oven. Grate the garlic onto the pan, and add the remaining 1 tablespoon olive oil and the lemon juice. Use a spoon to gently toss it all together (separating any grated garlic that clumps together). Serve immediately.