loud roaring noise when decelerating between 55-70 mph

Usually if a roaring noise is heard during acceleration or deceleration only (one or the other) it could be the rear differential as this is one of the symptoms of a failing ring and pinion (rear end)

You may want to check to ensure that 4wd is not engaged and also verify that the 4wd sensor is still good. If your vehicle is not 4wd you may want to have the wheel bearings checked. It may also be your universal joint, check to make sure you don't have any slop in it. If you do replace it. Hope this helps to narrow down the issue.

pinion brg. is gone south, causing to much backlash