It's the title of the song from Adele. I wonder what "Rolling in the deep" means.
According to an interview from Rolling Stone magazine:
...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.
(I found the quote here, haven't found the original source.)
According This Article Here "Rolling in the deep" means Being deep in love and experiencing everything that entails.