Preheat oven to 400 degrees F. Line a small baking sheet with parchment paper.
In a small bowl, whisk together brown sugar and spices with a fork. Add apple slices and toss to coat. Spread apples onto prepared baking sheet.
Place oats on a separate small baking sheet. Place both baking sheets in the oven. Remove the oats after 5 minutes. Allow the apples to bake for another 5 minutes (10 minutes total). Cool oats and apples for about ten minutes.
In a blender, pulse the oats until finely ground. Add the roasted apples, apple juice, and vanilla extract to the blender and blend until smooth. Pour into a glass and serve immediately or chill for later.