再给大家提供一条来自
songfacts.com 的“靠谱”解说：
Adele could have called this song "We Could Have Had It All," but that would have been fairly typical and sound like something Whitney Houston would sing. Instead, she used another line in the chorus that is curious to American listeners, adding some intrigue to the song. So what does the phrase "Rolling In The Deep" mean? She described it to Rolling Stone as an, "adaptation of a kind of slang, slur phrase in the UK called 'roll deep,' which means to have someone, always have someone that has your back, and you're never on your own, if you're ever in trouble you've always got someone who's going to come and help you fight it or whatever like that. And that's how I felt in the relationship that the record's about, especially 'Rolling in the Deep.' That's how I felt, you know, I thought that's what I was always going to have, and um, it ended up not being the case."
via
http://www.songfacts.com/detail.php?id=21312不过如下面的评论所说，to roll deep 的含义在地区间有区别。我觉得怎么理解完全取决于个人。歌手能提供的只是这个字眼罢了。