<p>The effectiveness of role assignment strategies in asynchronous discussion groups (ADGs) has been a subject of debate, with varying empirical evidence. This study aimed to comprehensively evaluate the impact of such strategies on students’ learning engagement, outcomes, and perceptions. We implemented five distinct roles (starter, responder, challenger, summarizer, and social tutor) and conducted a quasi-experimental design involving 40 college students across eight groups. Over a period of five weeks and three learning tasks, the experimental group, employing the role assignment strategy, demonstrated significantly higher levels of positive emotions and higher-order cognitive engagement compared to the control group. Despite increased instances of confusion, the experimental group held significantly positive perceptions of the discussion strategy and the collaborative learning environment. Importantly, the role assignment strategy positively moderated the relationship between positive emotions and learning outcomes, suggesting its potential to enhance the depth of student engagement and satisfaction in ADGs.</p>