Overview
When an organization decides to organize cross-functionally into development teams, the orchestration of development efforts and tracking of dependencies usually becomes more than a given discipline leader can manage alongside their primary responsibilities. In light of that, dedicated roles and persons to fill those becomes more normative.
Team of Teams Roles
Two roles serve to facilitate the mechanics of Team of Teams, the Team Steward and the Product Steward. In addition to those two roles, each discipline whose practitioners are members of the teams are also represented in the Team of Teams leadership group.

Team Steward
At the Team of Teams level, the Team Steward role focuses on the health of the Portfolio Backlog and Portfolio Roadmap, as well as supporting team-level Team Stewards with the effectiveness of team-level Backlogs and Roadmaps.
Product Steward
The Team of Teams Product Steward is primarily responsible for steering the vision for the products or parts of a product being developed by the member teams, and ensuring that the Portfolio Roadmap is aligned with what their stakeholders are looking to accomplish.
Discipline Stewards
It is crucial that a Team of Teams have leadership representation for each of the disciplines represented in the teams. These discipline stewards ensure that the content of the Portfolio Backlog reflects the standards, practices, and direction that each of those practices has set. This helps ensure that teams are not unintentionally drifting off-course with qualitative aspects of their work such as scalability, privacy, design norms for UX, and others.
Team of Teams Roles – Typical Product Development

For many product development contexts, Engineering, Quality, and UX/Design are the disciplines that need representation within Team of Teams leadership.