In a small saucepan, melt butter over low heat.
Once melted, add the flour and stir continuously until smooth.
Cook the mixture on low heat for 10-15 minutes, stirring occasionally, until it becomes golden brown.
Add curry powder, garam masala, paprika, cumin, cinnamon, cayenne pepper (if using), and black pepper.
Mix well until the spices are evenly distributed.
Remove from heat and let the mixture cool slightly.
Transfer the roux to a mold or container and allow it to set in the refrigerator for 1-2 hours before using.