Mercs taken to another planet.

[Rimmerdal]

LF a story about a small squad of mercs that were picked up by aliens. Dropped on world that the highest society at the time was Roman.
They had to help defeat the Romans and consolidate as "Winter" was coming which lasted a very long time almost wiping out civilization.

I know. I remember bits and pieces of military ones.

Umm. Any good ones along the line of 'Path of the Necromancer' or 'A warlock and a paladin walk into a bar'?