Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or lightly grease it.
In a large mixing bowl, combine the rolled oats, protein powder, baking powder, ground cinnamon, and salt. Stir until well mixed.
In a separate bowl, whisk together the applesauce, almond milk, maple syrup, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and mix until just combined. If using, fold in the chopped walnuts and raisins.
Divide the batter evenly among the muffin cups, filling each about 2/3 full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.