roast beef should never be eaten cold. beef, in general, loses much of its panache when it cools. the guys at john’s deli know this to be true, insisting on nuking your roast beef order whether you ask them to or not. if you’re wise, you ask the guys to plop on melted mozzarella (or “motz,” in the new yawk lingo) and ladle a river of beef-flavored gravy over everything. the result? the best roast beef ‘wich i’ve ever had, bar none.