Preheat oven to 425 degrees. Arrange bacon in a single layer on a large rimmed baking sheet. Bake until browned and somewhat crispy, about 15 minutes. Remove bacon from the cookie sheet and add brussel sprouts in a single layer, sprinkle with salt and pepper. Roast until they begin to brown, about 15 minutes
Remove sheet from oven and toss in apple. Return to oven; roast until brussel sprouts are browned and tender and apple has softened, 10 to 15 minutes.
Toss vegetables with vinegar, and serve immediately.
**You can adjust the amounts on the bacon and apples. If you love bacon, add more. Same with the apples.