Canon-Update Info
Rory is made of plastic. He is a plastic human-person. An auton, but with the consciousness of Rory Williams. His earth-leeching ability will still be used to heal wounds, but now it's more of a self-repair type of thing. He will also have the gun-hand and extra-powerful hearing that comes with being an Auton, and he will be dropping the reality-altering ability.
As for the canon-update, there really isn't all that much to change. We know that Rory is pulled into the cracks in time and space, that this erases him from all of history. We also know that The Alliance, a group of aliens made up of quite a few of the Doctor's alien enemies and other people that he has encountered in his timeline, have created a set of Autons in the shape of Romans from a memory in Amy Pond's mind. That this memory contained a recollection of Rory at a halloween party where he was dressed as a Centurian, so the Alliance also created an Auton Centurian that looks exactly like Rory Williams.
Somehow, Rory's consciousness and personality were fused into this Auton duplicate. The Auton, in a sense, became Rory Williams. Rory himself described it as "Well, I died and turned into a Roman. It's very distracting."
It was in this form that Rory re-met Amy and the Doctor. While the Doctor did remember Rory, and expressed some...confusion and concern as to his return, Amy did not remember him at all. Not even after Rory saved her from being 'upgraded' by a Cyberman with some fairly adept 'swording'.
The Doctor, however, encouraged Rory to keep pushing Amy, to try and get her to remember. Unfortunately for everyone, this was when The Doctor was being lured into a trap by the Alliance. A box called the Pandorica that would keep him inside of it forever.
Unfortunately for Rory, it was at this point that they would discover the root of what had brought him back to life. The fact that he, and the other Romans of the Legion, were Autons. So while Amy did, fairly quickly, remember who Rory really was, and while Rory was able to stop his auton programming, he was NOT able to stop it in time. Amy Pond was shot with his gun-hand before he could stop himself.
Fortunately for him, quite a lot of time-travel shenanigans clued him and The Doctor into the fact that if they placed Amy inside the Pandorica for 2,000 years, she would stay on the verge of death. So that is exactly what they did. The Doctor used a time-travel watch to jump 2,000 years into the future, and Rory...well.
Rory waited. And waited. And guarded the Pandorica. For 2,000 years, he was known as the Lone Centurian. He guarded the box against major catastrophies, against men who toted it around on tours. All the way until it became a part of the British Museum, and then he became a Security Guard for real. Waiting until the time was right for Amy Pond to wake up.