Preheat oven to 400 degrees Fahrenheit. Prepare your favorite single 9" pie crust and bake until puffy, 10-15 minutes. Remove and cool until ready to use. Reduce oven to 325 degrees.
Combine 4 tablespoons melted butter with ¼ cup brown sugar and toss carrots and sweet potatoes in the mixture to coat.
Place vegetables in a single layer on a baking sheet and roast until tender, 25-30 minutes turning halfway through. Remove and cool. Then place in a blender or food processor.
Meanwhile, melt the remaining 4 tablespoons butter in a small saucepan over medium heat. Add brown sugar, ½ teaspoon salt, and ½ cup heavy cream then stir to combine. Bring to a boil then simmer 4 to 5 minutes or until thick and luscious. Remove from heat and cool.
Add remaining 1 cup cream, spices, eggs and half the caramel sauce to blender with carrots and sweet potatoes. Blend until smooth and pour into prepared pie shell. Bake in the center of preheated oven until center is set, 45 to 60 minutes.
Let cool completely before cutting and serving with whipped cream and reserved caramel sauce. Garnish with carrot tops.