Open source software (OSS) has become foundational to modern computing, yet its sustainability depends as much on social organization as on technical excellence. Governance defines how contributors collaborate, how roles are created, described and coordinated to sustain participation at scale. Studies have shown that weak or opaque role structures can lead to burnout, turnover, and declining engagement, as communities struggle to balance autonomy with accountability. Despite the recognized importance of governance, empirical work examines isolated cases or relies on prescriptive frameworks rather than analyzing the artifacts where governance is formalized. This paper addresses that gap through a multi-project study of governance documents from OSS projects hosted on GitHub. Through these artifacts, we extract all defined roles and decompose them into four dimensions: scope, decision rights, obligations, and life-cycle rules. We then map these textual structures to a catalog of skills and apply both computational and interpretive clustering to reveal patterns of role differentiation and overlap. Our results reveal organizational (strategic) and operational (technical) roles and expose the blurred boundaries between them. We identify strong role drift, where similar titles conceal distinct responsibilities across projects, while different labels often encode the same function. Skill-based clustering exposes composite roles that merge coordination, mentoring, and technical stewardship, grounding the Maintainer Paradox as a pattern. These findings evidence OSS governance as an institutional infrastructure that balances structure and flexibility, codifies community memory, and reveals how open collaboration is sustained through the written design of roles.