Technological innovation is simultaneously a technical process and a socio-political process, and the fate of technological innovation can be determined by the roles performed by key individuals participating in the process and their influence. While the existence of key innovation roles emerging in the innovation process as a means to promote technological innovation and their impact on innovation have been widely discussed, research on how innovation efficiency is affected by role differentiation has rarely been conducted. This study presented a theoretical framework for analyzing the antecedents and outcomes of key innovation role differentiation in the new product development process from a contingency theory perspective. Empirical results based on data from 91 new product development projects across 37 firms in the electronics, information and communications, machinery, and chemical industries showed that: first, role differentiation is positively related to organizational complexity; second, role differentiation itself has a positive impact on innovation processes and outcomes; and third, the fit between role differentiation and organizational complexity has a positive impact on innovation processes and outcomes. These findings empirically demonstrate the contingent relationship that role differentiation in the innovation process must be aligned with organizational complexity in the firms where innovation occurs. Based on the analysis results, the study explored theoretical implications of the findings along with practical measures and policy implications for effective technological innovation in Korean firms, and suggested future research directions.