Preheat the oven to 375 degrees F (190 degrees C). Place cashews on a baking sheet.

Bake in the preheated oven until warmed through, about 10 minutes.

Meanwhile, stir rosemary, margarine, brown sugar, salt, and cayenne pepper together in a large bowl.

Pour warm cashews into the rosemary mixture and toss to coat. Serve warm or allow to cool to room temperature.