Cloud robotics augments robots by various cloud computing resources. Although it is regarded as a revolutionary paradigm in robotics, building a cloud robotic application is still a complex task today. Great efforts have to be made to develop the robotic-oriented cloud services, deploy them onto the cloud and integrating robotic software with them together. In this paper, we propose a cloud platform, micROS-cloud, which supports the direct deployment of Robot Operating System (ROS) software packages. The packages can be transformed into Internet-accessible services automatically. With the mechanisms named on-demand instantiation and container-based isolation, multiple robots can access such a cloud service simultaneously, even if the corresponding ROS package is originally designed just to serve a single robot. With micROS-cloud, general ROS applications can be easily migrated into the cloud robotic environment, and a lot of existing ROS packages in the robotic community can be transformed into o cloud services quickly. A prototype of this platform and the experiments on it involving multiple robots have validated the effectiveness of our work.