Preheat oven to 200°C (approximately 400°F).
Dissolve espresso powder in 1-2 tablespoons hot water. Let cool. Beat egg white until not completely stiff, then stir in espresso, sugar, and cinnamon. Fold in nuts. Spread nuts on a baking sheet lined with parchment paper. Roast, turning occasionally, about 20 minutes.
Remove nuts from oven, let cool and serve dusted with powdered sugar.