In a small bowl, whisk together the dressing, sherry, and pepper until well blended.
In a large bowl, toss the potatoes and peppers together with ¼ cup of the dressing mixture. Arrange the potatoes and peppers in a single layer on a parchment lined baking sheet. Bake for 15 minutes or until the potatoes have softened and are crispy. Remove from the oven and let cool.
In a large bowl, add the lettuce, roast beef, sweet potatoes, peppers, pecans, and bacon. Toss with enough of the remaining dressing to evenly coat.
Serve garnished with the Parmesan cheese.
For safe meat preparation, reference the USDA website.