SELECT    
	roles.principal_id                           AS RolePrincipalID
 	,roles.name                                  AS RolePrincipalName
 	,database_role_members.member_principal_id   AS MemberPrincipalID
 	,members.name                                AS MemberPrincipalName
FROM sys.database_role_members AS database_role_members  
JOIN sys.database_principals AS roles  
  ON database_role_members.role_principal_id = roles.principal_id  
JOIN sys.database_principals AS members  
  ON database_role_members.member_principal_id = members.principal_id