How should I mention my role in my resume?
It would help if you could clarify some things from your post. But, I will venture to say that if this is a college project I do not recommend you include it as work experience (as it is not actually work experience).
If you really want to include it, a better place to do so would be in some sort of "Relevant Projects" section on your resume. As it was a collective effort, you can put it something like: "Co-designed, developed, tested and deployed an IoT project about [...] with other three team members."
Also, remember to include such project only if you are applying to a job that has something to do with IoT, etc., otherwise it will be just noise in your application.