The sequence of descriptor layouts and push constants that can be used by a pipeline is specified by creating a vireo::PipelineResources and using it when creating the pipeline.

You can't do much with a pipeline resource on the CPU side beside creating them, they are exclusively used to allocate data needed by the graphics API (the real descriptor set layouts/root signatures).

Creating and using a pipeline resources

Pipeline resources are created using vireo::Vireo::createPipelineResources and you use them in a vireo::GraphicPipelineConfiguration struct.