01 - Set the oven temperature to 350°F and prepare a baking sheet by lining it with parchment paper.
02 - Place almonds, cashews, and pecans in a large mixing bowl.
03 - Drizzle olive oil over the nuts and toss to coat thoroughly. Add sea salt, smoked paprika, garlic powder, and cayenne pepper, mixing well to season evenly.
04 - Spread the seasoned nuts evenly in a single layer on the prepared baking sheet.
05 - Roast in the oven for 18 to 20 minutes, stirring once halfway through, until golden brown and aromatic.
06 - Immediately after roasting, sprinkle with fresh rosemary if desired and toss gently to combine.
07 - Allow the nuts to cool completely before serving or storing in an airtight container.