Unmanned Aerial Vehicles (UAVs) are used, in addition to the military, in various civilian applications. Some UAV applications may involve multiple UAVs working and collaborating together to achieve a common goal. Developing such applications is time and effort consuming due to the heterogeneity of UAVs and the complexity of the operations involved. These UAVs are usually monitored and controlled using peer-to-peer radio frequency communications. This requires either direct links between the UAVs and the ground station, or through multiple hops between them. This approach suffers from many limitations and it forces the user(s) to be at the mission location. In addition, it restricts the mission's area within the range of UAV communication. Overcome this issue, we propose a platform architecture that integrates the UAVs with the cloud computing paradigm, so that UAVs become as servers and part of the cloud. We modeled the UAVs in a Resources-Oriented Architecture (ROA); they provide their resources and services through the uniform interface RESTful HTTP. For distributed UAVs, we propose a broker architecture to separate the requester side from the provider side. The main purpose of this broker is to assign the requested tasks to the suitable available UAVs. The separation of responsibilities facilitates easier development of UAV applications on top of the platform.