Mix red peppers, olives, thyme, and vinegar in small bowl for relish. (Can be made 1 day ahead. Cover and refrigerate.) Reserve 2 tablespoons goat cheese for garnish. Spread remaining goat cheese on toasted baguette slices. Divide arugula among toasts. Fold roast beef slices to fit toasts; place atop arugula. Sprinkle beef slices lightly with salt and pepper. Top each with 1/3 teaspoon reserved goat cheese and small dollop of relish. Arrange crostini on platter and serve.