1. Combine cream cheese and horseradish in a bowl. Mix until smooth.
2. Spread about three tablespoons of cream cheese mixture on 1 tortilla. Place spinach leaves over the cream cheese. Place roast beef over the spinach and sprinkle with a layer of shredded cheese. Roll the tortilla tightly and wrap it up in clear plastic wrap. Repeat with remaining ingredients. Refrigerate the wrapped rolls at least 4 hours. Can be made a day ahead.
3. To serve, just slice and eat. This can be used as an appetizer or a sandwich. It also travels well for picnics. Just throw the wraps in an ice chest and cut them up when you are ready to eat.