Your professor is absolutely correct. Roman latrines were quite sophisticated and are extremely common, we find public latrines all over every single major city. Here's one in Ephesus. Here's one at Ostia--an old TA I once had has a very nice picture of that particular one (it's quite large) but she's in the picture so I don't think I should post it. They're literally everywhere, and the legionary forts of the Principate usually show traces of field toilet not unlike the public latrines of the cities. Mind you, this is what public latrines looked like, private toilets within houses obviously did not have rows and rows of seats, although they were basically smaller versions of the same setup