The reason this stuff is so fascinating is that you wonder if they didn't have ships well capable of crossing the atlantic.
I have frequently wondered that myself. I think they were far more advanced than the current generations give them credit for.
Romans In Rio?
Science Frontiers ONLINE
No. 28: Jul-Aug 1983
http://www.science-frontiers.com/sf028/sf028p01.htm
In 1976, diver Jose Roberto Texeira salvaged two intact amphorae from the bottom of Guanabara Bay, 15 kilometers from Rio de Janeiro. Six years later, archeologist Robert Marx found thousands of pottery fragments in the same locality, including 200 necks from amphorae.
Amphorae are tall storage vessels that were used widely throughout ancient Europe. These particular amphorae are of Roman manufacture, circa the second century B.C. Much controversy erupted around the finds because Spain and Portugal both claim to have discovered Brazil around 1500 A.D. Roman artifacts were distinctly unwelcome. More objectively, the thought of an ancient Roman crossing of the Atlantic is not so farfetched. Roman wrecks have been discovered in the Azores; and the shortest way across the Atlantic is from Africa to Brazil -- only 18 days using modern sailing vessels.
(Sheckley, Robert; "Romans in Rio," Omni, 5:43, June 1983.)