SELECT C.Name,U.UserName,R.RoleName,R.Description,U.AuthType FROM ReportServer_SQL2008_Prod.dbo.Users U
JOIN ReportServer_SQL2008_Prod.dbo.PolicyUserRole PUR
ON U.UserID = PUR.UserID
JOIN ReportServer_SQL2008_Prod.dbo.Policies P
ON P.PolicyID = PUR.PolicyID
JOIN ReportServer_SQL2008_Prod.dbo.Roles R
ON R.RoleID = PUR.RoleID
JOIN ReportServer_SQL2008_Prod.dbo.Catalog c
ON C.PolicyID = P.PolicyID

Note- For a specific report use below code
SELECT C.Name,U.UserName,R.RoleName,R.Description,U.AuthType
FROM ReportServer_SQL2008_Prod.dbo.Users U
JOIN ReportServer_SQL2008_Prod.dbo.PolicyUserRole PUR
ON U.UserID = PUR.UserID
JOIN ReportServer_SQL2008_Prod.dbo.Policies P
ON P.PolicyID = PUR.PolicyID
JOIN ReportServer_SQL2008_Prod.dbo.Roles R
ON R.RoleID = PUR.RoleID
JOIN ReportServer_SQL2008_Prod.dbo.Catalog c
ON C.PolicyID = P.PolicyID
WHERE c.Name = @name of your report
ORDER BY U.UserName