Preheat oven to 425 degrees F (220 degrees C). Grease a large roasting pan with butter.
Combine potatoes, apples, carrots, and sweet onion in the bottom of the roasting pan and sprinkle with rosemary.
Season roast with salt and pepper on all sides and rub with sage. Dust with flour on all sides.
Heat 2 tablespoons oil in a large skillet over medium-high heat and brown roast on all sides, about 2 minutes per side. Add roast to the pan.
Combine hard apple cider, apple cider vinegar, 1/4 cup oil, and honey in a bowl and whisk well; pour over roast and vegetables. Cover with a lid or aluminum foil.
Roast in the preheated oven for 20 minutes. Reduce heat to 350 degrees F (175 degrees C) and bake until an instant-read thermometer inserted into the center of the roast reads at least 150 degrees F (65 degrees C), about 1 hour more. Remove from oven, cover, and allow to rest for 30 minutes.