This work presents a technique for designing of real-time systems embedded applied to multi-robots scenarios, exploiting High-Level Architecture (HLA) standard for interoperability and simulation platforms, and Robot Operating System (ROS) with Robot-in-the-Loop simulations. The goal is to integrate existing consolidated standards and tools, rather than separately design and later hardly integrate. Through HLA, heterogeneous simulations can be synchronously co-simulated, enabling the joint execution of consolidated embedded system design tools for dedicated tasks, like, network simulation, circuits and algorithms design, etc. In parallel, ROS simplifies the task of creating complex robots across a wide variety of platforms. A bridge has been developed to provide an interface among HLA and ROS, exchanging data and keeping both synchronized. As proof of concept, the Ptolemy framework for Embedded System design has been integrated to Stage, a ROS compatible robotic simulator for 2D environments. This innovative integration has been successfully developed and validated, which enables future generalizations and opens opportunities to co-simulation of diverse tools for designing of embedded and robotics systems.