There was certainly a connection at this time between Rome and China, through the Silk Road but there is no conclusive evidence of any similar battle... Romans were certainly traveling to China to sell their wares... but those are merchants with a few guards to protect them on their way, not an army.
According to this Variety article by Maane Khatchatourian, the battle the film is centered around is purely fictional:
Set in 206-220 A.D., the movie focuses on a key (fictional) battle between Rome and China’s Han Dynasty. It follows Chinese officer Chan, who’s framed and later enslaved, and Roman soldier John Cusack, who escapes to China after rescuing the Prince. The two cross paths in the Western Desert.
The Wikipedia article on Sino-Roman Relations states there may have been a "hypothetical military contact" between the two groups but there is no proof of it:
After losing at the battle of Carrhae in 54 BCE, an estimated 10,000 Roman prisoners were displaced by the Parthians to Margiana to man the frontier. Some time later the nomadic Xiongnu chief Zhizhi established a state further east in the Talas valley, near modern day Taraz. Taking up these two strands, Dubs points to a Chinese account by Ban Gu of about "a hundred men" under the command of Zhizhi who fought in a so-called "fish-scale formation" to defend Zhizhi's wooden-palisade fortress against Han forces, in the Battle of Zhizhi in 36 BCE. He claimed that this might have been the Roman testudo formation and that these men, who were captured by the Chinese, founded the village of Liqian (Li-chien, possibly from "legio") in Yongchang County.
However, Dubs' synthesis of Roman and Chinese sources has not found acceptance among modern historians on the grounds of being highly speculative and reaching to too many conclusions. Although DNA testing in 2005 confirmed a predominantly "Caucasian origin" of a few inhabitants of Liqian, this influx of Western genes could be explained just as well by transethnic marriages with other peoples along the silk road. A much more comprehensive DNA analysis of more than two hundred male residents of the village in 2007 showed a close genetic relation to the Han Chinese populace and a great deviation from the Western Eurasian gene pool. The researchers conclude that the people of Liqian are probably of Han Chinese origin. Moreover, the area lacks clear archaeological evidence of a Roman presence.
Though, as you'll notice, even this hypothetical event occurred much earlier, in 36 BCE, which is 242 years before the beginning of the range of time the film was set (206 CE/AD).
