According to Arby's, the meat in an Arby's roast beef sandwich is roast beef. Furthermore, according to the company's "Slicing up Freshness" campaign, the meat is hand sliced, using a meat slicer, by people and not machines.
Arby's was founded in 1964 by two Ohio brothers who decided to establish a sandwich shop that would compete with burger chains by offering freshly sliced roast beef sandwiches instead of hamburgers. The company reports that the classic roast beef sandwich is its best selling item, followed closely by the roast beef 'n' cheddar sandwich. In 2012, the Arby's began slicing and serving roast turkey in addition to roast beef and other selections.