Analyzing the influence of social media on the learning process is no longer a novel idea; however, due to its importance for students and consequently for teachers, research continues to explore the pedagogical potential of social media. The main objective of the present study was to analyze the influence of teacher roles (guide or facilitator) on students' social participation in Twitter and their perceived academic experience. The sample consisted of 525 future teachers, all of the Master's degree students at Spain's National Distance Education University (UNED). We used a mixed triangulation design, a theoretical model, quantitative methods (descriptive analysis and contrast of means) and qualitative methods (content analysis following the principles of grounded theory). Our results showed that the teacher's role as a facilitator exerted a more positive influence on how students assessed their experience and on their participation on Twitter than the role as a guide. We conclude that the use of social media sites in education offers a motivating and satisfying framework that is not provided by other more traditional means such as forums, and that a role that facilitates independent learning is a better strategy when using social media in the classroom.