Rome is a great wonder of ancient times, of how a mere small village then in 300BC could rule most of Europe & North Africa, became an empire & brought forth idealism & capabilities to latter descendants & fellow Humans spread Worldwide even today.
However, the most relevant idiom from Rome was ' When in Rome, do as the Romans do'. Romans were an exclusive free democratic People back in those days, learnt from the Greeks about democracy & do not take kindly to strangers, even foreign kings whom begged for Roman support, as they knelt to no one before Republic Rome was destroyed by petty feuds from others within.
The idiom's relevancy lays in the keyword - Assimilation. If one could speak Latin, behaved as free man & follow Rome's social norms of those days, contribute to Rome, he/she would be welcomed. Such traits. in context such as adoption of new lingo & culture, would help foreigners assimilate into any country in this modern World that they had fled from, which had not brought them opportunities they desired, & worse-must not bring those FAILED cultures into any land that they had escaped from into a new nation that they seek to progress, to further contaminate & destroy the future of their next generations...