Cook your bacon in a large skillet. When your bacon is done, drain on paper towels and then chop into bite size pieces and set aside. Reserve 2-4 tablespoons of your bacon fat.
In that same skillet, heat 2-3 tablespoons bacon fat and add the russet and sweet potato cubes. Stir them around to coat well, salt and pepper to taste, and put a lid on for 10 minutes. (this will steam the potatoes and help them to cook faster)
Take the lid off, stir them around and cook for an additional 5-10 minutes longer. Don’t stir too often; you want the potatoes to get a nice brown crust.
Cut your Brussels sprouts in half (or quarters if they are large) and toss them in 2 tablespoons oil.
Move the potatoes to one side of your pan and add your Brussels sprouts. Add more bacon fat, or oil if needed.
Add your chopped sage to the pan, and cook an additional 10 minutes until brussels sprouts are cooked through (you can always add the lid to steam them a bit if they are on the larger side and taking longer to cook).
When Brussels and potatoes are cooked through, top with your rotisserie chicken, reserved bacon bits, and scallions.
Serve with a side of gravy and cranberry sauce (and topped with an egg) if desired.