The role theory plays in research work cannot be over-emphasized. A theory that is apt gives direction to research work in explaining, organizing, analyzing, and predicting phenomenon and showing their relationships in order to enhance understanding. Despite these roles played by theory, upcoming scholars and students many at times fail to use theory that is apt in their research work, while some skip to adopt any theory in their research, even when it is necessary to adopt one. Thus, leading to disjointed and poor research work. Lack of good theory and/or lack of its correct application instantly de-links the relationship and blurs the understanding of research questions, variables, and hypotheses, which theory integrates to give a coherent and holistic view of phenomenon, and answering the question of "why" the phenomenon is the "way" it is. Explanatory and qualitative research approaches were employed. Secondary data were collected from books, journal articles; internet materials, etc. were used in analyzing the roles theory plays in research work. The findings are (1) that the purpose of theory is to explain, describe, analyze, and predict phenomenon to aid understanding (2) a good theory that is apt and well applied gives clarity and logicality to the problem understudy (3) theory in research is like a bridge that links concepts, variables, and hypotheses. The paper recommends among other things that scholars/teachers should devote more chapters or contribute more papers in journal specifically on theory.