The answer to the second question of the day: what inventions would you take back to Roman times if you had the chance, is as follows.
Remember they had no electricity so most of our stuff would be useless, but here are some things I think would work. Bicycles - they might be a bit rough, particularly in the tire department, but they had some pretty good engineers and also jewelers who could make the chain. Then there would be wind boards. Just think of a regiment of centurions sailing across the Mediterranean on windsurfers!
I think we know a lot about hygiene which would be worth passing on. The propeller would no doubt ease the efforts of all those galley slaves and finally, make the Olympic games licensed and take a cut of the concessions! The last one was from a business friend of mine.