The phrase "assumes the role of" suggests that someone is taking responsibility or control over something. However, there are many antonyms for this phrase that convey a different meaning. Instead of assuming a role, one could forsake the role, reject it, or even pass it on to someone else. Other options include denying, disowning, or disavowing the role altogether. Alternatively, one could opt to share the role, cooperate with others, or even collaborate with others to jointly assume the role. Whatever the opposite approach, there are many ways to express a lack of willingness to take on a particular role.