The social relations model (SRM) is commonly used in psychological research to analyse interdependent data from round-robin designs, where all members of a group rate each other. Based on the recently suggested social relations confirmatory factor analysis (SR-CFA), we present general formulas for determining the reliability of composites of round-robin judgments and also derive simpler variants when specific restrictions are applied to the parameters of the SR-CFA model. In the unidimensional case, this results in an omega-type reliability measure, which can be converted into an alpha-type reliability measure through further restrictions. We also discuss how standard errors of the reliability coefficients can be obtained, illustrate the suggested methods using an empirical example, and we examine the suitability of the estimation approach in a small simulation study. Finally, we discuss questions for future methodological research and how the person-level composites are related to other SRM effect estimates proposed in the SRM literature.