Preheat the oven to 375°F (190°C). Roll out the pie crust and place it on a greased or parchment-lined baking sheet or pizza pan.
In a bowl, mix the apple slices with granulated sugar, brown sugar, cinnamon, nutmeg, cornstarch, and lemon juice. Stir until apples are coated evenly. Spread the apple mixture evenly over the crust.
In a separate bowl, combine oats, brown sugar, flour, and cinnamon. Stir in the melted butter until the mixture becomes crumbly. Sprinkle the streusel topping over the apples.
Bake for 25-30 minutes, or until the crust is golden brown and the topping is crisp. Remove from the oven and drizzle with caramel sauce. Let cool slightly before slicing. Serve warm with vanilla ice cream for an extra treat!