DiscoJen said:I don't believe there is a standard roller that you can simply buy a replace.
An alternate to those nasty easily broken plastic rollers on the DI is to use a washer. Cut through one side with a dremel or a hacksaw, twist it over the stud on the regulator, then pinch the washer back so that it is flat. Lube track/washer and that holds pretty well. I can't remember what size washer; I usually had the track out and took it with me to test fit washers.