Simulation, robotics, and Radio Frequency Identification (RFID) technology have significant roles in the new industrial revolution, and their application are key aspects of making Industry 4.0 a reality. Developing efficient use cases in Industry 4.0 almost always requires accurate simulation tools to be used in the digital world. The problem of simulating RFID readers for robotics in environments where high populations of RFID tags exist is addressed in this paper. This paper will discuss the design of an RFID system plugin based on Robot Operating System (ROS) and Gazebo simulator and the probability-based model on which the plugin is based. To assess the performance of the proposed system model, the simulation results of the designed plugin are compared with experiments. We also prove that the proposed simulator is flexible enough to be used on any robot platform, including aerial and ground robots. We show initial results of the simulation of having an Unmanned Aerial Vehicle (UAV) and a Unmanned Ground Vehicle (UGV) equipped with an RFID reader, navigating in an environment in which RFID tags have been placed. The robots will be reading tags in different map layouts using RFID antennas, with different orientations. We compare the simulation and experimental results in terms of the total unique tag readings vs. time, for various map-layouts. Finally, we show how this plugin can be used in robotics research by using it to simulate a novel, RFID-based stigmergic navigation strategy. We illustrate, the accurate navigation of the UAV using the proposed plugin.