How to Make It
Stir together rosemary, granulated sugar, salt, and cayenne pepper in a small bowl. Set aside. Cook the bacon in a large skillet over medium, turning occasionally, until crisp, 14 to 18 minutes. Transfer bacon to a plate lined with paper towels; reserve for another use. Pour drippings through a fine mesh strainer into a bowl; discard solids. Wipe skillet clean.
Heat 3 tablespoons of the drippings in the skillet over medium. Add cashews, pecan halves, almonds, hazelnuts, soy sauce, and reserved rosemary mixture. Cook, stirring often, until nuts are coated and sugar has melted, 2 to 4 minutes.
Transfer nuts to a baking sheet lined with parchment paper; spread in one layer. Bake at 350°F until toasted, stirring occasionally, 10 to 14 minutes. Cool completely, 30 minutes. Store in an airtight container up to 1 week.