Roast beef is the classic Arby's staple with a unique, unconventional preparation that locks in moisture and delivers a powerful umami punch. This, paired with a sharp, melty, and gooey cheddar cheese sauce is already a winning combination. Arby's zesty red ranch is the mysterious special sauce that completed the trifecta and dazzled our tastebuds; despite its name, it's a sweeter, tangier, and tomato-based sauce.