Prepare the Carrot Cake

1. Preheat the Oven: Start by preheating your oven to 350°F (175°C). Line a 10×15-inch jelly roll pan with parchment paper and lightly grease it to prevent sticking.
2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt. Set aside.
3. Prepare Wet Ingredients: In a large bowl, beat the eggs and sugar until light and fluffy. Add the vegetable oil and vanilla extract, and beat again until fully combined.
4. Combine Wet and Dry Ingredients: Gradually add the dry ingredients to the wet mixture, stirring gently until fully incorporated. Be careful not to overmix.
5. Add Carrots and Nuts: Gently fold in the grated carrots, walnuts, and raisins (if using).
6. Spread the Batter: Pour the batter into the prepared pan, spreading it evenly with a spatula.
7. Bake: Bake the cake for 12-15 minutes, or until a toothpick inserted in the center comes out clean.
8. Cool: Remove the cake from the oven and immediately place a clean kitchen towel on your counter. Lightly sprinkle powdered sugar over the towel and carefully turn the cake onto it. Peel off the parchment paper. Starting from one end, roll the cake up with the towel inside, then set it aside to cool completely.

Prepare the Cream Cheese Filling

1. Beat the Cream Cheese and Butter: In a medium bowl, beat the softened cream cheese and butter together until smooth and creamy.
2. Add Powdered Sugar and Vanilla: Gradually add the powdered sugar, one tablespoon at a time, beating well after each addition. Stir in the vanilla extract and salt.
3. Chill: Once the filling is smooth and fluffy, place it in the fridge while the cake finishes cooling.

Assemble the Carrot Cake Roll

1. Unroll the Cake: Once the cake has completely cooled, carefully unroll it from the towel.
2. Spread the Filling: Spread a generous layer of cream cheese filling over the entire surface of the cake, leaving a small border along the edges.
3. Roll it Back Up: Starting from one edge, gently roll the cake back up, making sure the filling stays in place. Be careful not to apply too much pressure or it might crack.
4. Chill: Wrap the rolled cake in plastic wrap and chill in the fridge for at least 1 hour to allow the flavors to meld and the cake to set.

Serve and Enjoy

Once chilled, slice the cake roll into 1-inch slices and arrange them on a serving platter. The delicate swirl of carrot cake and cream cheese filling will be revealed with each slice, impressing your guests and family alike.