In the west, the position and meaning of artists have changed quite a lot. I suppose in antiquity, the artist was less important, than the motif, which was often god kings or religious symbols, and the artist more of a craftsman, than what we perceive today.
In medieval times, the artist can also be a satirist of a kind, mocking both the high and the low.
Then later, the artist became somewhat of a celebrity, culminating in the Renaissance, where the artist was probably THE most important cultural phenomenon. We also have the perception of the artist as being able to capture the divine or later, the sublime, so the artist is a transcendental figure.
Which roles have artists played in Chinese society over the millenia?
This is quite a general question, so I'll do my best to respond...
To define the role of the artist in Chinese culture through the millennia is quite a complex undertaking. One must consider the medium at hand, the ruling dynasty, and the religious/social/political connotations of a work of art.
Take handscrolls for example. These operate quite differently than a book in terms of spatial dynamics (this source relates to Japanese art), linguistic organization, and the active relationship that the reader has with the scroll itself. Handscrolls were produced by an array of collaborators, but perhaps the most well-regarded was the calligrapher. In China, art is intertwined with poetry and calligraphy. Visual works are therefore synonymous with the literature produced, as Chinese calligraphy is a rhythmic, visual language. Often, as the reader would extend their arms out to hold the scroll and move from right to left, the calligraphy would act as a precursor to the following visuals; the two would act hand in hand together to successfully communicate with the reader. In this context, the role of the artist is also the role of the writer.
Artists also had imperial ties to the ruling dynasty (like European courtly artists, such as Velazquez). These dynasties are broadly defined by the following: Semi-Legendary; Ancient China; Early Imperial China; Middle Imperial China; and Late Imperial China. Wall paintings or frescoes were created to commemorate military or political victories of these dynasties. The Mogao Caves are immensely popular and organized by dynastic rule. The styles between these dynasties have a slight variance, always with ideological/religious undertones (I will touch upon religion in the paragraph below). The Tang Dynasty is regarded somewhat similarly to that of the Renaissance and was considered a cultural, imperial, and cosmopolitan golden age.
The Dunhuang Caves are overwhelmingly Buddhist, with the introduction of Mahayana Buddhism in the late 2nd or the 1st century CE through the Silk Road (where these caves are located). These caves operated as commemorative spaces, places of worship, and tombs. Artists employed upaya (that is, skillful means) to promote Buddhist teachings and distill difficult-to-comprehend concepts into visual human terms.
It actually appears that in hanging scrolls, handscrolls, paintings, etc. that Early Imperial Chinese artistry was better attributed than that of Medieval Western artistry. I would challenge your point situating a western medieval artist strictly as a satirist. While this was common, art during this period (especially that in the Byzantine Empire) was dedicated to Christianity. From this, we can interpret that religion and art are deeply correlated on a global level.
There is a lot of complexity with Chinese art, as one can tell. It is near impossible to generally classify the role of the artist, especially due to the wide range of mediums. As I stated in the beginning, one must take a formal and contextual approach in interpreting the role of the artist. At all points in time, it appears that the artist serves as the medium for ideologies. Art often serves to actualize the manifestation of theory, sociopolitical dimensions, religion, ideology, etc.
Here are some excellent sources found on JStor:
Hay, Jonathan. "The Mediating Work of Art."
Murray, Julia. "Buddhism and Early Narrative Illustration in China."