Rollers themselves are cheap. What changes the bill is how many need replacing and what kind you want in. Nylon rollers run quieter and don't need the lubrication steel does, but they cost more per unit - on a 2002-era door with standard track, upgrading from steel to nylon is usually the call homeowners make once they're already paying for a truck to come out.
Rio Vista's median household income sits at $86,970, noticeably below the wider service area's $139,567. We mention that because it's the honest context for why a lot of Rio Vista jobs we quote are partial sets - replacing the four or six rollers that are actually grinding, not the full ten, when the rest still have life left. That's a legitimate way to do this job. It just means you'll likely be back for the rest in a few years, not a decade.
We don't publish a flat number here because we haven't got one specific to this town's travel and labor mix. What we can tell you is the parts cost is a small fraction of the visit - the trip and the labor carry most of it.