Assign roles to the user “reader” with a query?

Just execute the query:

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'bulkadmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'dbcreator'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'diskadmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'processadmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'securityadmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'serveradmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'setupadmin'

EXEC master..sp_addsrvrolemember @loginame = N'reader', @rolename = N'sysadmin'

The set of command will assign to the user reader different roles.