Quintillian refer : http://en.wikipedia.org/wiki/Quintilian
there is none, but you might be thinking of an aqueduct. Correction: there are many Roman "things" that start with Q. Here are some: quadra--a square, quadrans, a coin, quadrigae, a racing chariot, quaestor, a treasury official, qualus, as wicker basket, quercus, the military crown of oak leaves, and quirites, the formal connotation of Roman citizens. There are many more.
quiz
Quartz and quantum theory are science words. They begin with the letter Q.
which African American has a last name that starts with Q? which African American has a last name that starts with Q?
Quill
Suzi Quatro is a singer. Her name begins with Q.
Qatar
Quinton
Quanika
Quail Urine
quince
Q isn't a number in Roman Numerals, but if you mean "What is q in the Roman Alphabet?", then I don't know.
Quinton McCracken
quilt mabey
Quin sanet
The Queensboro Bridge is a busy bridge in New York City. It begins with the letter Q.
Quetin Blake