The last one called safe is always someone who could be in the dance off due to their position on the leaderboard, to add a bit of tension. For example, they were never going to leave AJ to be called safe last this week, because once it got down to her and Adam everyone would know that there would be no way it could be her in the dance off. However, as Rose was in the bottom half of the leaderboard there was a chance it could have been her. I don’t think it means that she only just escaped the bottom two though, I think she’s getting enough votes to put her higher than that. So while they say it’s in no particular order, they’re never going to leave an obviously safe person to be called last as it removes all the tension.
Obviously that doesn’t work later on in the series when only the good people are left and it’s all really close anyway!