Heat oven to 350°F. In medium bowl, stir together carrot, radish, cucumber, sriracha sauce, vinegar, lime juice and cilantro. Set aside.
Arrange bread slices on ungreased cookie sheet. Bake 6 to 8 minutes or until lightly toasted.
In small bowl, stir together mayonnaise and five-spice powder. Spread 1 teaspoon mayonnaise mixture on each bread slice. Place a quarter slice roast beef on each bread slice. Top with 1 teaspoon vegetable mixture.