Preheat oven to 325°F and line a baking sheet with parchment paper.
Combine Brazil nuts, pumpkin seeds, cashews and coconut flakes in a bowl and toss well.
Drizzle with oil and toss to coat evenly.
Add chopped rosemary and sea salt (if using) and toss again.
Spread the mixture in a single layer on the prepared baking sheet. Roast for 12–14 minutes, stirring once halfway through, until lightly golden. Watch carefully — coconut flakes can brown quickly.
Let cool completely on the pan before storing. Store in an airtight container at room temperature for up to 2 weeks.