The Roswell remains were the remains of the corpse of an interdimensional being.
In 1947 a UFO crashed in Roswell, New Mexico, and the body of an unknown being was found therein. The corpse was recovered by a team of US military, who brought in a group of civilian specialists to investigate the site and remains. One of those researchers was Indiana Jones, and he was later sworn to secrecy.
In 1957 Indiana Jones and George McHale were captured by Soviet agents. Taken to Hangar 51, the pair were forced by Irina Spalko to locate the crate where the remains were held. Jones, remembering that the corpse had magnetic qualities, used gunpowder and shotgun pellets to follow their trail and locate it.
Once the crate was located, the Soviet troops opened it to verify the contents, and were astounded at the strong magnetic properties. Jones used their distracted attention to try to regain control of the situation, but McHale revealed himself as a double agent. Unable to stop the Soviets, Jones managed to escape, but Spalko gained control of the remains, and her team later examined them.
Spalko took the remains with her to Peru and Brazil when she was looking for the Crystal Skull of Akator. After capturing Jones, who had found the crystal skull, and bringing him to the Soviet encampment, Spalko showed to Jones that the creature's skeleton was as crystalline as the skull.
Behind the scenes
Since Oxley explained to the others that the being(s) with the crystalline skeletons in the temple Temple of Akator were interdimensional beings who came from and returned to the "space between spaces", it can be concluded that the Roswell remains also were remains of an interdimensional being.
In the James Rollins novelization of the film, the body of the interdimensional being was dissected by Spalko and a team of surgeons at an unspecified location three hundred miles away from the place where Jones was interrogated by the FBI and briefed by General Bob Ross.
- Indiana Jones and the Kingdom of the Crystal Skull
- Indiana Jones and the Kingdom of the Crystal Skull novel