I'm trying to have the following folder structure with Dsc Class Resources in DscResource1 and DscResource2. Everything I try with NestedModules, etc.. I keep getting errors from the LCM "Failed to create an object of PowerShell class IssRobocopy". Everything works fine if I just keep the module name files and the resource name file the same. This seems very restrictive.
For class-based resources, all of the class definitions need to be in a single psm1 file (which should be referenced by the RootModule element in your manifest, and probably safest to also name it DscModule.psm1). I don't know if / when that's going to change.
However, you can write other PowerShell functions in separate files, and just have the stuff in DscModule.psm1 be the simple shell of the classes (much like a schema.mof file in the old resources). Something like this:
It's fine to have multiple classes in one module. The class definitions just all have to be in the same PSM1 file; you can't currently split them into multiple ps1 files and dot-source them from the PSM1, or anything along those lines.