The problem of simulating an RFID system for robotics is addressed in this paper, which presents the design of a ROS Gazebo RFID system plugin that enables the simulation of the RFID readers-antennas mounted on robots reading RFID tags in the environment. The plugin is based on a model based on probability of detection which simulates the behavior of the complete RFID system, comprised of readers, antennas, and tags, in the Gazebo simulation platform. We also show, by comparing simulation and experimental results, that the proposed solution is able to fairly accurately model the read rate of the actual RFID system. Finally we present an application scenario of a UAV performing an inventory mission at high altitudes.