Unless someone weighed the tongue of the trailer, I would say the 420 lbs is based off of the gross vehicle weight of the trailer, which means it is not that heavy empty.
At and empty weight of 3480lbs with say a 1000lbs of gear and water... keep in mind you shouldn't travel with much water unless you have to and this doesn't include grey or black water. You will be at 4480lbs roughly. You can safely pull that with a rover, and I wouldn't even think about it without a weight distribution hitch and sway bars. The first time you try it without, and then with you will never go without again. But here comes the part that no one wants to here, The Rover is only a 100 inch wheel base. Basically that means that you shouldn't pull anything longer than 20 foot long, now of course you can get around this with a good sway system. And yes I have towed longer items without sway, but it wasn't fun. If your serious about towing something long and you want to do it safely I would recommend buying a real good sway system.
http://www.hensleymfg.com/ either that or buy some real good term life insurance and PM me for my full legal name ans SSN and I will gladly be the beneficiary.