Step 1: Preheat the Oven

1. Preheat the oven to 425°F (220°C). Line a large baking sheet with parchment paper.

Step 2: Prepare the Buffalo Mixture

1. In a small bowl, whisk together buffalo sauce, olive oil, ranch seasoning, and black pepper.

Step 3: Coat the Potatoes

1. In a large bowl, toss the diced potatoes with half of the buffalo mixture until evenly coated.

Step 4: Roast the Potatoes

1. Spread the potatoes in a single layer on the prepared baking sheet.
2. Roast for 60-70 minutes, flipping halfway through, until crispy and golden brown.

Step 5: Marinate the Chicken

1. While the potatoes roast, toss the chicken pieces in the remaining buffalo mixture and let them marinate.

Step 6: Assemble and Bake

1. Once the potatoes are done, lower the oven temperature to 400°F (200°C).
2. Transfer the roasted potatoes to a greased 9×13-inch baking dish.
3. Spread the marinated chicken evenly over the potatoes.
4. Sprinkle with shredded cheddar and Monterey Jack cheese.

Step 7: Final Bake

1. Bake for 20-25 minutes, or until the chicken is fully cooked and the cheese is melted and bubbly.

Step 8: Serve & Enjoy

1. Remove from the oven and let it rest for a few minutes.
2. Garnish with chopped green onions and serve with sour cream and extra buffalo sauce, if desired.