Ciao Danielle and welcome to our community! I'm not sure about Italo train schedules; we are ItaliaRail2 and work with Trenitalia trains and their schedules. I'm not sure how Italo schedules coincide with the national railway's schedules.
The high-speed train schedules with ItaliaRail tickets aren't yet available for October 1 direct travel from Venice S. Lucia to Rome Termini, but if you go to our Train Timetables page18 and click the blue "follow" button in the upper right corner, you'll get a notification every time any new routes are released. That way you can book as soon as the schedules are out.
Hope this helps! Happy trip planning!