Roast the shallots, stirring occasionally, until they are golden brown, about 20-30 minutes. While the shallots are roasting, get the potatoes ready. Toss them with remaining 1 1/2 tablespoons oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a bowl, and then, when the shallots are caramelized, add the potatoes to shallots.