I think you might be swapping RDMA with RoCE - RDMA can happen entirely within a single node. For example between an NVME and a GPU.
Within a single node it's just called DMA. RDMA is DMA over a network and RoCE is RDMA over Ethernet.
Within a single node it's just called DMA. RDMA is DMA over a network and RoCE is RDMA over Ethernet.