How to Make It
Preheat oven to 450°F. Arrange the chicken and sweet potatoes side by side in a single layer on a large rimmed baking sheet. Season with the sage, salt, and pepper and drizzle with 2 tablespoons of the oil, tossing to coat. Lay the bacon on top of the sweet potatoes.
Roast until a meat thermometer inserted into the thickest portion of a thigh registers 165°F, 20 to 25 minutes.
Meanwhile, toss together the watercress, lemon juice, and the remaining 1 tablespoon of olive oil and season to taste with salt and pepper.
Serve the chicken with the sweet potatoes and salad, with the bacon crumbled over the top.