lbs sweet potatoes, peeled and each cut lengthwise into 6 wedges (4 large)
Put oven rack in middle position and preheat oven to 450°F.
Generously butter a 13 by 9 inch glass baking dish.
Heat marmalade and orange juice in a 1-quart heavy saucepan over moderately low heat, stirring, until marmalade melts. Stir in Angostura bitters, salt and pepper and remove from heat.
Pour marmalade mixture over potatoes in a large bowl and toss gently to coat, then spread in 1 layer in the baking dish. Bake, uncovered, turning potatoes over once or twice, 30 minutes, then continue baking without turning until the potatoes are tender and the tops are slightly caramelized, about 30 minutes more.
Let stand 10 minutes before serving to allow glaze to thicken.