Preheat oven to 425F.
In a large bowl, mix the sweet potatoes with the spices. Line a baking sheet with tin foil, and spread the sweet potatoes on top, in one layer.
Roast the sweet potatoes until they are soft, about 15 minutes.
In the meantime, in a large bowl, mix the dressing ingredients.
Remove the sweet potatoes from the oven and toss them in the bowl with the dressing. Coat all pieces with the dressing but be careful not to mash the sweet potato.
Return to the baking sheet, turn the oven to hi broil and broil for a few minutes, until the sweet potatoes are roasted and crispy.
Remove from the oven and try not to finish everything while you wait for it to cool off.