Stir together first 3 ingredients. Spread mixture evenly on wraps. Layer each wrap evenly with roast beef, lettuce, and cheese slices; sprinkle each with nuts and green onions. Roll up tightly. Cut in half diagonally.
Note: For testing purposes only, we used Boar's Head Brand Pub Style Horseradish Sauce and Toufayan Bakeries Wheat Wraps.