Heat 2 tablespoons olive oil in a small skillet over medium heat; add 2 chopped garlic cloves and 1/2 teaspoon each cumin seeds and kosher salt and cook 2 minutes. Stir in 1 tablespoon brown sugar, the juice of 1/2 lemon and a pinch of red pepper flakes. Toss with 1 1/4 pounds halved Brussels sprouts on a baking sheet. Roast at 450 degrees F until tender, 18 to 24 minutes. Toss with torn cilantro.