I got rolled back the other day as well, here are the steps as they unfolded:
1) i found a nice ethereal dusk with no sockets in hell, finished my runs in that game.
2) a bud of mine logged in and I went into a game which he joined.
3) we talked a sec and went into a trade window.
4) i showed him the dusk and he was like um so its not so impressive....
5) I told him to hang a sec then exited the trade, and cut some sockets into it with the cube
6) It then became a pretty decent canidate for some merc gear with 4 open sockets.
7) I showed him again and we sat in the trade window for a few minutes chatting.
8) I noticed it seemed I was lagging all of a sudden and we both got C/I'ed with a full rollback.
9) when I could rejoin a game I checked and my nice 4os eth dusk had reverted to its original unsocketed state, and original defense.
***Note the item was found in hell, and socketed in normal where the rollback occured.***