Coat the brussels sprouts evenly with salt, pepper, and olive oil. Bake for 25 minutes at 400 degrees. (If you like them softer bake for longer).
Meanwhile, in a small saucepan, combine the cranberries, maple syrup, and orange zest. Cook over medium-low heat, stirring, until the cranberries break down and thicken, about 10 minutes.
In a medium skillet, cook the butter over medium heat until golden, about 3 minutes. Remove from the heat, add rosemary and stir into the cranberry sauce. Transfer the cranberry sauce to a bowl, add the brussels sprouts and toss. Season with more salt and pepper and extra rosemary.
Serve and enjoy!
Note: Simply double or triple the recipe for a larger party.