Heat oven to 450°F. In large bowl, whisk together orange juice, oil, cumin seeds, ¾ teaspoon salt, and ¼ teaspoon pepper. Add broccoli and garlic and toss to combine.
Divide broccoli and garlic between 2 rimmed baking sheets and roast, rotating positions of pans halfway through, until broccoli is just tender and charred in spots, 14 to 17 minutes. Smash garlic with fork on pan, combine vegetables on 1 sheet pan, scatter orange zest on top, and toss to combine.
