The vomitorium was not a room for vomiting.
The story that Romans threw up in special rooms during banquets so they could keep eating is a modern invention. A vomitorium was the passage through which an amphitheatre 'spewed out' its spectators: the Colosseum could empty its roughly 50,000 visitors within minutes this way. The term comes from the writer Macrobius around AD 400.
Useful: A word that sounds like something is not yet evidence that it meant that.
Source: en.wikipedia.org