There is a science fiction/fantasy writer named David Drake who has written a number of short stories featuring Roman soldiers. Several told of a Roman legion that had been defeated and the survivors sold into slavery. Their new masters were from a Galatic trading empire that was restricted to using low-tech methods to conquer planets so they could trade with them.
Eric Flint has written and/or edited a lengthy series based on the idea a typical WV town winds up suddenly in S. Germany in 1632, middle of the 30 Years’ War. They decide to start the American Revolution a little early.
Does a good job of showing the quite significant limitations of superior technology, in combat and economics, especially when available only in small quantities.
As the saying goes, quantity has a quality of its own.
There is another guy Weber who wrote a similar story(He wrote the Honor series) about some English knights plucked off a sinking ship from the 8th century who were used for the same purpose. Overtime, the adaptability of the English knights allowed them to turn the tables on their captors and take over the ship and start a rebellion of sorts against the ruling galactic consortium.
Ranks of Bronze, about survivors of crassus army. I liked it quite a bit. Birds of Prey was set in roman-era almost as a placeholder. Poul Anderson wrote a great deal in this general time-frame, both from the roman side and stories set in germania during the roman era.