I'm not completely familiar with these roads, but I currently live near somerset, nj and have driven down that way a few times. Here's a link to a NJ bike maps webpage for the area you're looking to ride. Check out the "plainfield" map after looking at the map key or legend to know what the colors mean. I'm pretty new to riding and found the maps to be very helpful in avoiding heavy traffic areas.

hope that helps a little! Good luck, stay safe.