Objectives Clarifying the roles of teaching assistants (TAs) is crucial for enhancing their support effectiveness. This study aimed to explore the differences in expectations regarding the roles of TAs between general education teachers and TAs in Chinese primary classrooms as well as the factors associated with these differences. Methods A sequential explanatory mixed-methods approach was employed. A total of 465 general education teachers and 400 TAs were surveyed to provide quantitative data, while five teachers and five TAs were interviewed to provide qualitative data. Results The quantitative survey revealed significant differences between teachers and TAs in terms of their overall expectations regarding TA roles as well as differences in the dimensions of personal care and classroom support. In particular, teachers scored significantly higher than TAs with regard to personal support; however, they scored significantly lower than TAs with respect to overall expectations and classroom support. The qualitative investigation revealed that these differences in role expectations were associated with internal (i.e., perceptions of the purpose of TA support and knowledge of student abilities) and external factors (i.e., professional training from schools and communication between teachers and TAs). Conclusions This study enriches the international literature on the role expectations of TAs in an inclusive education context and has important implications for their role clarification.