To teach programming effectively, instructors must possess diagnostic skills and the ability to provide individualized interventions. This requires a deep understanding of students’ mental models and common misconceptions in programming, along with the capacity to assist students in refining their mental models where necessary. In our approach, we utilize videos depicting secondary school students’ programming processes to train pre-service teachers in diagnostic skills. While these videos facilitate initial diagnoses, they alone cannot confirm them. Therefore, a complementary method is essential to teach diagnostic conversations and interventions effectively. To address this need, we developed tasks that aim at these skills by incorporating role-playing of students with misconceptions. Our research focused on evaluating pre-service teachers’ engagement with these tasks and their reported outcomes. Our findings reveal that it is hard for them to get into the mind of a student who holds misconceptions. They also report that trying to do so is useful for understanding students’ thought processes. The results suggest that role-playing tasks can foster the transition from theoretical knowledge about mental models to the practical ability to simulate their effects. In this way, our tasks contribute to bridging the gap between theory and practice in teacher training.