Preheat the oven to 375 degrees F. Brush a 9" x 13" baking dish with the butter. Combine the sugar and spices in a bowl. Place the nectarines, pitted side up, in the baking dish. Drizzle with the rum or brandy and lemon juice; sprinkle with the brown sugar mixture. Roast the nectarines, uncovered, 10 minutes. Remove from the oven. Use a small spoon and baste each nectarine with the liquids in the pan. Roast 10 to 15 minutes more, or until nicely glazed and tender. Serve the nectarines over ice cream with the liquids in the baking dish drizzled over top.