​These roast beef sandwiches are so simple because of the deli meat. It's already cut into thin slices for you so all you have to do is add it to your sandwiches. But, if you have leftover roast beef, you can use that as well. My dad has a meat slicer, so we're easily able to slice a full roast into sandwich slices. If you don't have that, you can actually shred the roast beef and use it that way.