Heat the oven to 350 degrees. Place the sweet potatoes on a baking dish and bake for about 1 hour, or until just tender. Remove from the oven and let cool completely. Remove the skins from the potatoes and cut into medium dice. Reserve.

Combine the sweet potatoes, mangoes, red pepper, onion and scallions in a bowl. Toss with enough vinaigrette to moisten the salad. Season with salt and pepper to taste.