This recipe is easy to make, and the vegetables can be roasted in the oven or, if it’s too hot for cooking indoors, they can be roasted on the grill.
Soak the rosemary and garlic in oil – (garlic will tend to burn in a 400F roasting-temperature oven or on the grill; you can stave off the burning by adding moisture to the garlic cloves with a soak in olive oil). Mix 1 tsp of the oil, slivered garlic and chopped rosemary, and set aside for 15-30 minutes.
Preheat the oven to 400F (or preheat the grill on medium-high heat).
With a sharp knife, cut off the bottom/stem end of the Brussels sprouts (optional). This may make the outer leaves of the vegetables fall off, but will, on the positive side, remove the tough part of the vegetable. Any leaves that fall off will crisp up in the roasting process, and will be like seasoned, crunchy chips (yum).
In a mixing/salad size bowl, mix the remaining olive oil, Brussels sprouts, salt and pepper. Toss so that vegetables are well-coated. Transfer the sprouts to a rimmed baking sheet, spreading them across the pan in a single layer. If cooking on the grill, transfer seasoned, oiled Brussels sprouts to a lightly-oiled grill pan, or enclose in a packet of aluminum foil.
Roast the Brussels sprouts in the oven (or on the grill) for 35 minutes. After the first 15-20 minutes, sprinkle the oil-soaked garlic and rosemary over the sprouts. Toss lightly to combine, and continue roasting. Stir Brussels sprouts once or twice during the roasting time, so that all sides brown nicely.
Transfer roasted vegetables to a serving dish, sprinkle with a little sea salt, and serve immediately.
Make ahead: Can also be roasted ahead and served cold or at room temperature.
Optional: serve Brussels sprouts with a cruet of balsamic vinegar so that diners can add a splash as desired.