ROS 1 and ROS 2 are two widely-used robotic middleware. One of their essential features is to enable two robots with the same middleware, ROS 1 or ROS 2, to directly connect and collaborate. However, two robots running two different middleware can only communicate by additionally using one of the bridge solutions available in the robotic community. It is even more challenging when deploying these robots as part of an OPC UA-based industrial testbed. The first challenge is to network the robots with other OPC UA devices. Second, a testbed environment sometimes requires a robot to join the system rapidly and with minimal configuration for quick experiments. While addressing the above needs, this paper presents an approach to bridge ROS 1 and ROS 2 robots to an OPC UA PubSub network. The approach derives from the actual experiences in developing an OPC UAbased robotic testbed for Industry 4.0 research.