Preheat oven to 400°F and line two rimmed baking sheets with parchment paper or Silpat® baking mats. Set aside.
In a large bowl, toss apples, fennel, red onion, sage, 2 tablespoons of olive oil, and balsamic vinegar.
Season with salt and black pepper, to taste, and combine until the apple and veggies are completely coated.
Spread the apple mixture onto one of the prepared baking sheets and roast on the bottom oven rack for 10-15 minutes, or just until the veggies start to soften and develop a bit of color.