"Turn the other cheek" was in response to Hebrew custom. Carry the pack the extra mile was in reference to, Do more than what is expected of you. Yes, Romans could expect/order anyone to carry their pack for a mile, but no more.
It was the law. If a Roman soldier hit a Jew, they were to turn the other cheek. A soldier could order a Jew to carry his pack for a mile.. Get it? He could take a Jew's cloak.