Delta Airlines have round trip airfares travelling from Houston (HOU) to Rome Italy (FCO) for $474, making one stop in Atlanta, their hub. Unfortunately too, that leg of the flight is basic economy. Delta's basic economy allows a carry-on bag in addition to one small personal item but not advance seat assignment and no paid or comp'd upgrades allowed.
Departs Oct 22-24, 26, 30-31; Nov 1-3, 6-10, 12-15, 20-30; Dec 1-7, 9-12
Returns: wide availability returns thru Dec 24, 2018
Use dates and book it on Delta Airlines [delta.com]
. It's $10 more on other OTAs.