In a small bowl, combine 2 tablespoons prepared horseradish, 1/2 cup mayonnaise, 1/4 cup sour cream, 1 teaspoon Dijon mustard, 1 teaspoon apple cider vinegar, 1/2 teaspoon honey, 1/4 teaspoon salt, and 1/4 teaspoon freshly ground black pepper. Whisk until smooth and taste; adjust heat/sweetness by adding more horseradish or honey in 1/4-tsp increments. Chill at least 10 minutes to let flavors meld (can be made up to 24 hours ahead).

Beef Roll-up Assembly

Prepare arugula

Place 2 cups packed baby arugula in a medium bowl. Drizzle with 1 tablespoon extra-virgin olive oil and 1 teaspoon lemon juice. Add 1 teaspoon salt and 1/2 teaspoon freshly ground black pepper. Toss gently to coat. If using the optional 1 teaspoon honey for balance, add it now and toss again.

Lay out roast beef

On a clean work surface or cutting board, arrange 12 slices of thinly sliced roast beef in a single layer, slightly overlapping if needed so each slice provides a full wrap.

Assemble each roll-up

Spread about 1 teaspoon of the prepared horsey sauce down the center of each roast beef slice (adjust to taste). Place a small handful of the dressed arugula (about 1–2 tablespoons per slice) on top of the sauce in the center. If using microgreens, add a few on top for extra texture.

Roll and secure

Carefully roll each slice away from you into a tight cylinder, enclosing the arugula. Secure with a toothpick if desired. Repeat with remaining slices.

Finish and garnish

Arrange roll-ups seam-side down on a serving platter. Spoon any extra horsey sauce into a small dipping bowl for the platter. Sprinkle 1 tablespoon chopped fresh chives or parsley over the roll-ups for color. Optionally, add extra arugula or microgreens around the platter. Serve immediately, or chill up to 1 hour before serving.