Here is what very large hail (two inches or more) looks like on radar.
The orange oval is the area where hail was likely falling at 5:17pm EDT. The two orange arrows indicate a non-meteorological echo known as a "hail spike." There is no precipitation falling along the spike. It is an artifact of the way the radar senses the hail. Unfortunately, the Roanoke WSR-88D does not have dual-polarization as yet so I cannot show you what the hail would look like on that type of display.
There is also a tornado warning (purple polygon) in effect on that storm.
Update: Saturday, 9:15pm CDT. Via Facebook here is a photo of some of the hail from this storm.
[caption id="attachment_8047" align="aligncenter" width="899" caption="Hail in Franklin Co., Virginia. Exact location unknown."][/caption]