I'm back home now and decided to just delete my last comment and make a new.

Most everything we have from Roman authors are copies of copies, original texts rarely survive. Library's held manuscripts of these works but much later than they were actually written. Some of the oldest manuscripts we have are from the 5th and 6th century. Here is more information on the recovery of history, and here is information on the oldest manuscript found of Pliny the Younger's works.

The only scrolls I've found that may be written by the original author were found at Herculaneum in the villa of the papyri in 1752. They were preserved during the eruption of Mt. Vesuvius in 79 A.D. It's a library containing mostly Epicurean texts. Most notably by Philodemus who is believed to have arrived in Italy around 80 B.C. There are multiple copies of certain scrolls which leads some people to believe that a section may have been his personal library. They are slowly copying these works, but due to their condition, it is a little difficult. The work being done is called the Philodemus Project.

As far as I know that is the closest you'll find to an original work by a Roman author. I hope this somewhat your answers question.

edit: bad link, re wording, fixed date

You might also be interested in this thread from a few months ago, which touches on this subject closely. See especially this link, cited by /u/GeorgiusFlorentius.

To add to the above question, what writing mediums would the Romans from this time period have used?