When it comes to antonyms for the phrase "assume role of" there are several options that come to mind. One possible antonym could be "relinquish role of," which would imply giving up or surrendering a position or responsibility rather than taking it on. Alternatively, "reject role of" could also be considered an antonym, as it suggests a refusal to take on a particular role or position. Other options might include "abdicate role of" or "disavow role of," both of which imply a similar sense of relinquishing responsibility or authority. Ultimately, the choice of antonym will depend on the context in which the phrase is being used and the specific shades of meaning that need to be conveyed.