Nothing. The Roswell, NM "UFO' is a myth.
UFO Crash at Roswell was created in 1991.
According to sheep rancher William Brazel, the debris was spread over 3/4 mile longwise and serveral hundred feet wide.
Roswell Yes and Ufo's No
roswell
Demi Moore
The UFO that crashed there in 1947
Roswell, New Mexico is located in the Chihuahuan Desert.
Secrets of UFOs - 2006 Roswell UFO Crash What Really Happened at Roswell 1-4 was released on: USA: March 2006
Encounters with the Unexplained - 2000 Roswell UFO Crash What Really Happened at Roswell 1-3 was released on: USA: 8 September 2000
If you mean Roswell, I am not certain there ever were any actual UFO sightings. Just an armload of Project MOGUL debris and sixty years of tell tales spun around it.
Europe's Roswell UFO Crash at Aberystwyth - 2009 was released on: USA: 1 March 2009
UFO Files - 2004 Mexico's Roswell - 2.13 was released on: USA: 12 December 2005