Preheat the oven to 425 degrees F. Scrub the sunchokes under cold running water and slice 1/4-inch thick. Add the sunchokes and garlic to a roasting pan or baking sheet and toss with the olive oil so the bottom of the pan and the sunchokes are lightly coated. Add more olive oil a tablespoon at a time if you don't feel like the vegetables are coated enough, but not too much; you don't want them swimming in olive oil. Sprinkle with the salt and rosemary. Bake for 15 to 20 minutes, until the sunchokes are tender inside, like a potato.