code: def get_roles(osa_repo_dir, commit, role_requirements):
      
      repo = Repo(osa_repo_dir)
  
      checkout(repo, commit)
  
      log.info("Looking for file {f} in repo {r}".format(r=osa_repo_dir,
                                                         f=role_requirements))
      filename = "{0}/{1}".format(osa_repo_dir, role_requirements)
      with open(filename, 'r') as f:
          roles_yaml = yaml.load(f)
  
      return normalize_yaml(roles_yaml)
docs: Read OSA role information at a particular commit.