As Jack lay dying at the end of 'Lost', a plane full of the Island ordeal survivors flew overhead in the Ajira jet to escape back to the mainland - Lapidus, Sawyer, Kate, Claire, Richard, and Miles. Nine were left behind on the Island - Hurley, Ben, Desmond, Rose, Bernard, Cindy and the kids, and you can't forget Vincent. (Come on - is there anybody who didn't well up when Vincent lay down beside Jack to keep him company as he crossed over? And wouldn't you have liked to have seen him in the church as well?)
Of course, I think the Island number quickly dwindled down to five once Desmond took Cindy and the kids back to civilization on board his boat, the Elizabeth. And within two years, I believe the Island tally was reduced by one more.
Jack's father Christian told his son that many of those gathered in the church didn't die for many years after Jack. But that wouldn't have held true for Rose.....
When she landed on the Island, Rose was suffering from terminal cancer. But something about the Island, Jacob's magic perhaps, beat back the Big C into remission. And she knew that should she ever leave the Island, it would kill her.
But I think it killed her anyway. Remember, when Desmond shut off the access to the energy of the Golden Light, a lot of its benefits were discontinued - Not-Locke's invulnerability, Richard's immortality, and if Jin and Sun had survived the submarine attack, there never would have been any more Kwon Kids to keep Ji Yeon company.
We have to add the healing powers enjoyed by Rose. I think within two years, her cancer would have come raging back; and without the proper facilities or medical experts to treat her, her chances may have been even less.
As for Bernard, I think he would have carried on, still staying on the Island even without Rose. I believe she would have insisted on that; no taking a quick way out to join her for ol' Bernie. And for a few years more, he had the steadfast and loving Vincent by his side, until the loyal Lab also passed away a few years later.