Combine sunchokes, 1 tbs olive oil, 1/4 tsp salt, and pepper in a large bowl; toss well to coat.
Heat 1 tbs oil in large skillet (cast iron is best) over medium-high heat
Arrange sunchokes, cut side down, in pan until they start to brown (about 5 minutes).
If using a cast iron skillet, arrange garlic and rosemary evenly over sunchokes. If using a regular skillet, transfer ingredients to a baking dish and arrange as described (but add a little additional oil to the dish to prevent sticking). Place cast iron skillet or baking dish in oven and roast at 375° for 40 minutes or until sunchokes are tender and deep golden.