Salvete,
Actually I wonder in how far the Romans themselves knew these little mottos and proverbs. Like Ericius remarks, some of them are from later times, and others were definitely not famous in the time they were written down or spoken. It also raises the question if they really needed a national motto and if they perceived themselves as a nation. The abstractum "nation" was invented in the 17th-18th century. Before that a country was simply the area ruled by a monarch (perhaps with the exception of Switzerland).
Shameless plug: at the collegium Historicum, you can find an essay by me on this nationhood question.
However, back to the topic at hand...
C.AeliusEricius wrote:DULCE ET DECORUM EST PRO PATRIA MUNDI
You mean "mori" instead of "mundi" (as in "it is sweet and honourable to die for one's country").
ALEA IACTA EST
C.AeliusEricius wrote:ROMANI ITE DOMUM [oops]
Hahaha, I didn't know that one. Better not to spread anti-Roman propaganda Erici
(for the not-so-latinate among us, this phrase means "Romans go home!").
C.AeliusEricius wrote:HANNIBAL AD PORTUS
Should be "ad portas" instead of "portus".
Valete bene!
Draco
Gn. Dionysius Draco Invictus