This paper aims to discuss the changing roles and competencies of a teacher in context of prevailing developments accomplished by the vast availability of social software, which have made easy the development of Personal Learning Environments (PLEs). This has been accomplished by an in-depth review of the literature on teacher's socially situated competencies and roles with regard to the tasks and guidance they provide to students shape their PLEs. Review process provides an insight of PLE research studies, constructivist learning theories, and teacher changing roles. The results of this study outline the roles that portray the importance of teacher competencies as role in Planning and Design, Instruction and Learning, Communication and Interaction, Management and Administration, and Use of Technology. (Contains 1 figure.)