If the EV3 can be treated as a generic Linux (which has the ROS installed on it), then you can use ROS codegen capabilities in External Mode with EV3.
NOTE: You need to have ROS installed on EV3 to have ROS deployment (or external mode) to work.
Able to generate code with ROS: https://www.mathworks.com/help/robotics/examples/generate-a-standalone-ros-node-from-simulink.html --> In this you need to setup the Hardware Implementation as stated for the External mode to work.
External mode with ROS: https://www.mathworks.com/help/robotics/ug/enable-external-mode-forrobotics-system-toolbox-models.html
If your EV3 is always connected to MATLAB (via some connection wifi/ethernet) then you can consider running ROS blocks in Robotics System Toolbox to work in Simulation. I.e., you can get the EV3 sensor data in Simulink and then publish it using ROS Publish block and monitor them using ROS Subscribe block -> Extract data (do some processing) and then visualize them -> Simulink Scopes.
Robotics Team @ Mathworks