Spray a 9x13-inch baking dish with non-stick cooking spray.
Using kitchen scissors cut each cinnamon roll into 6 pieces, evenly scatter them in the bottom of the prepared baking dish.
In a mixing bowl, whisk together eggs, milk, cinnamon, nutmeg and vanilla. Pour the mixture evenly over the rolls making sure they are all well coated.
Cover the baking dish with plastic wrap and refrigerate overnight or for at least 6-8 hours. Rolls will thaw and rise.
The next morning, preheat oven to 375 degrees.
Remove plastic wrap and bake casserole for 35-40 minutes or until the rolls are well browned on top. Note: If the rolls are getting too brown before being cooked all the way through, cover with foil and continue baking.
Remove the casserole from the oven and frost with the cream cheese icing from the cinnamon roll package or drizzle with maple syrup if desired.