I'm not sure how Mass inspections work but in PA basically a rotted rocker would fail if it has exposed sharp edges that could snag clothing on a pedestrian if you were to hit them. I've seen duct tape used over rust holes to pass. While it looks ghetto its legal in the technical sense of no sharp edges. I've also seen expanding foam sprayed in and left to dry then cut/shaped to match and painted over.
I agree new rockers is the best avenue but if you need to get it to pass until you can get to the body work being a bit creative might get you thru.