SlicerROS2 now supports ROS publishers and subscribers, Tf2 broadcasts and lookups as well as parameters (client). The robot visualization is built on top of the parameter client (to retrieve the URDF) as well as Tf2 lookups (to move the robot's links).
Each ROS communication mechanism is encapsulated in a MRML node. These can be used in C++ as well as Python. Some simple unit tests are included in the accompanying module ROS2Tests.
Detailed documentation is available on readthedocs: https://slicer-ros2.readthedocs.io/en/latest/