Brush a 15x10x1-inch baking pan with the cooking oil. Arrange the sweet potatoes in a single layer in the pan. Sprinkle with salt and pepper. Roast potatoes in a 425 degree F oven for 25 to 30 minutes or until tender. Remove pan from oven; let cool on a wire rack.
In a bowl, whisk together the salad oil, vinegar, maple syrup, and Dijon-style mustard.
Transfer sweet potatoes to a bowl. Sprinkle with parsley. Pour dressing over all. Toss gently to combine. Serve at room temperature. Makes 8 side-dish servings.