The development of teacher leadership is closely intertwined with the transformation of teacher roles. However, few studies have investigated how this concept, first developed in North America, is affected by teachers' role identities (RIs) in an Asian context. To this end, this study aimed to examine the effects of teachers' perceived role expectations (PREs) and RIs on their leadership behaviour. The sage teacher, professional teacher and labourer teacher framework was used for analysis, and 498 junior high school teachers in Taiwan participated in a survey. Structural equation modelling and bootstrap analysis were employed to analyse the data. The results showed that teachers' PREs as professional and sage teachers were more significant than for labourer teachers. Their RIs also presented the same pattern. Moreover, although teacher leadership is closely related to the development of teacher professionalism, of the three types of teacher roles, only the PRE and RI of the sage teacher can significantly motivate teachers to lead in direct and indirect ways.