W.M. Kirkland 
Ridden Through Fire [EPUB ebook] 

The commander of his regiment, Owen watched as one-by-one his men were taken by a flash of white light. Surrounded by fire and outnumbered, he has one chance for freedom. He takes it, only to be surrounded by the white light and finds himself far from home. When he sees a barn fire, he races toward it to help the horses trapped inside.

Nate watched as his friends found their Romans and paired off. He realizes his Roman has come when a man clad in Ancient Roman garb rides toward the barn and breaks down the door. Now, his Roman has come for him, but only if they can get through the fire.