Considering that the Samurai class had its distant roots in Chinese political structure, did China or Korea have a similar warrior class?
In China, there were warriors similar to ronin - the xia. As a link, I found only those regarding their philosophy or literature about them. GURPS Martial Arts (it's no solid historical work and I didn't manage to find any better source) states they were more like Robin Hood than Lancelot - they were not upper class like samurai.
Korean Hwarang are approximation of Samurai from the other side - they were upper class young men probably serving as warriors, but it's not their defining feature. In GURPS Martial Arts they are presented as very similar to Samurai, but when I consider what is written in Wikipedia, it might be just a myth.
There is a Chinese saying (in pinyin), "Hao tie bu da ding, hao ren bu dang bing." (Good iron is not used to make nails. Good men do not become soldiers.)
For most of Chinese history, soldiers were vilified, rather than honored. Hence, they would not generally be regarded as members of the upper class, which was occupied by landowners and philosophers.
Most of Korea, whose culture is more similar to China's than Japan's felt much the same way.