When thou art at Rome, do as they do at Rome.

When you are at Rome, live as Romans live.

si fueris Romae, Romano vivito more; si fueris alibi, vivito sicut ibi
[if you should be in Rome, live in the Roman manner; if you should be elsewhere, live as they do there]

When they are at Rome, they do there as they see done.

Concentrate every minute like a Roman—like a man—on doing what's in front of you with precise and genuine seriousness, tenderly, willingly, with justice. And on freeing yourself from all other distractions. (Hays translation)

What's Rome to me, what business have I there?

The Romans were stern and dignified, living hard, frugal lives and adhering to the traditional Latin virtues, gravitas, pietas, simplicitas, and adultery.

"Well, when in Rome," said Jurgen, "one must be romantic."

Do unto others as they do unto you.

When I am here I do not fast on Saturday; but when I am at Rome I do: whatever church you may come to, conform to its custom, if you would avoid either receiving or giving offense.

Every moment think steadily as a Roman and a man to do what thou hast in hand with perfect and simple dignity, and feeling of affection, and freedom, and justice; and to give thyself relief from all other thoughts.

Roman! be thine the sovereign arts of sway;
Nobly to rule, and make the world obey:
Give peace its laws; respect the prostrate foe:
Abase the lofty, and exalt the low.

(Romans in the age of the Caesars believed that putting on the right shoe before the left brought prosperity and good luck.)

Si fueris Romae, Romano vivito more;
Si fueris alibi, vivito sicut ibi.