How do I indicate collate order in Roxygen2?

How do I indicate collate order in Roxygen2?

Using roxygen2 documentation with devtools document function automatically
generates a Collate: field in the package DESCRIPTION, regardless of
whether or not it is necessary to load the package library files in a
particular order.
I'm working on a package with a bunch of S4 methods and want to be sure
the class definitions are loaded before any methods or other classes using
them, which I understand I can do with the Collate list, but I'm not sure
how to indicate this in the roxygen2 documentation format.
The roxygen2 manual makes some reference to an @import tag but that looks
like it actually imports code, for instance, for an example file.