Polycarbonate....

[Tristan Lall]

Polycarbonate has more friction than many other common engineering plastics. It wouldn't be anywhere close to my first choice for a roller, and I would be similarly wary of it for a sliding pad.

However, given that you don't really have to much choice (<R92> implicitly bans raw Delrin on the minibot, for example), and durability in the long term is not a concern, it's probably going to be fine.

Now, if you want, there's a way to exploit a loophole in the rule to enable you to use certain other plastics. Buy plastic fasteners, and modify them to your specifications.* (Keep the bill, to facilitate your explanation to the inspector that you started with a fastener.) You can probably figure something out to convert a Nylon bolt into an appropriate roller.

*I should note that FIRST's Q&A hasn't ruled on this strategy; while ordinarily they say things like aluminum sheet metal is allowed, implying that it doesn't matter if the final form on the minibot renders the part no longer a sheet, it's entirely possible they could decide to be inconsistent, and define a fastener as something that still works as a fastener, rather than something originally sold as a fastener.