Roast beef sandwich

The end of the deli roast beef that starts out looking like a giant bright red disc shaved into slices that drains and changes color over days locked in a plastic bag aging by the hour. It doesn't look pretty anymore. Shame to cook it. Too tough to leave intact, it must be chopped. There is no au jus. 

My bread is excellent but a sandwich from Taste of Philly across the street is better.