How Can I Use A Trigger For Rollback Transaction?

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SQL-Server-2008R2

hi i want to create a trigger for rollback transaction, for exampel user can not delete a record from TblParaCode.
please help me .
this is my code

Create Trigger [dbo].[Test01]
On  TblParaCode
AFTER UPDATE,delete
AS
begin
if ((SELECT paracode From TblParaCode where typecode=29) =2)
begin
  RAISERROR('Cannot delete this record.',16,1)

 rollback transaction
end
end

thanks.