Trim the ends off the baguette and then cut it into 4 equal-sized sections, approximately 6 inches each.
Cut each section in half, front to back, to create a top and bottom section, as shown in the photos.
Spread some of the horseradish sauce on the bottom piece of one section.
Top with one-quarter of the arugula, Provolone cheese, and sliced tomatoes.
Season with salt and black pepper, if desired, and top with two ounces roast beef.
Complete the sandwich by adding the top section of the baguette.
Repeat this process three more times with the remaining ingredients.
Serve immediately with your choice of sides or cover tightly with plastic wrap for a quick and easy lunch the next day. Enjoy!