The role of the project portfolio manager is to head the team responsible for project prioritization and selection. His responsibilities include:
- Assessing projects based on ROI and their alignment with the corporate strategy.
- Suggesting the best projects to the executives based on ROI, corporate alignment, and resource availability.
- Ensuring executed projects are still aligned with the corporate strategy.
- Deciding, along with other executives, on whether to kill a project or not during gate meetings.
I think the project portfolio manager should be a separate role, just because of the sheer amount of work involved in doing the above.