Ms Rosenberg, 44, is a vice-president at Warner Brothers Records, where she is publicist for Seal, k d lang and other musicians. Running interference for the label's big gun, however, consumes nearly two-thirds of her time - maybe more from this week, when Madonna's latest album, Erotica, is released, followed by the already notorious book of photographs - Sex - in which the celebrity photographer Steven Meisel purports to document everything that Madonna finds a turn-on. She will also co-star with Willem Dafoe in the thriller Body of Evidence, to open here next year; the film has an NC-17 ('no children under 17') rating because of its erotic content.
Ms Rosenberg sits on one of three 'aqua' chairs confiscated as souvenirs from the tour's 'Material Girl' number. She is wearing purple leggings and gold sandals. Her blonde hair is swept back on one side and fastened with a faux tortoise-shell comb. She could be mistaken for Madonna's mother.
'She calls me Mom sometimes,' Ms Rosenberg acknowledges. 'I'm completely maternal, very protective toward Madonna. She's strong in a lot of ways. But I know a lot of it is just a front. I try to teach her things the way mothers want to teach their children about life: patience, empathy and calm. And humour. Sometimes I just remind her: 'Let's not take any of this too seriously.' '
Ms Rosenberg met Madonna, now 33, in 1983, when the singer walked into her office wearing 'a black outfit with a hundred rubber bracelets on each wrist'. Madonna was then an unknown singer and 'dance artist' on the Lower East Side club scene, who had been recruited by Warner Brothers to cut two singles. The publicist was struck by Madonna's fearlessness. 'Maybe that's one of the things that impressed me early on,' Ms Rosenberg says. 'I'm filled with fears.'
During the early days of her career, Madonna would drop into Ms Rosenberg's office to use the phone and talk about her boyfriends. More recently, when Madonna was having a much-publicised affair with Warren Beatty during the filming of Dick Tracy, he turned to Ms Rosenberg for advice on dealing with his inamorata, who, he claimed, lived her life too publicly. 'He was into the publicity game of another era - so elusive and the chase and all of that. It's just not the way publicity is any more.'
The way Ms Rosenberg plays the game is by creating the illusion of openness. She has advised Madonna never to say 'no comment', a phrase that, in print, has the effect of making a celebrity appear guilty as hell. The task of dealing with unruly reporters also falls to Ms Rosenberg. She has refined the art of clever one-liners, which often serve to amuse while stopping the questioner mid-sentence. For example, asked to confirm a rumour that Madonna once stubbed out her cigarette on a boyfriend, Ms Rosenberg replied: 'She doesn't smoke; she sizzles.'
Each morning the publicist calls Madonna to, as Ms Rosenberg puts it, take her temperature. 'If I have to disrupt her time in the studio,' she explains, 'I have to know if she's in a bitchy mood.' Ms Rosenberg's power within the industry derives from the fact that she controls virtually all access to Madonna and has authority to speak on her behalf.
How does Madonna, a self-professed control freak, feel about delegating the responsibility of speaking for herself? 'We've worked together for years and years and years,' the star says of Ms Rosenberg. 'She understands the consequences of whatever she says. I'd say 99 per cent of the time it is what I would have told her to say. We're at the point where we're reading each other's minds.'
In 1985, when Playboy published nude photographs taken while Madonna was a photographer's model, Ms Rosenberg says the singer came into her office wailing that her career was over. Ms Rosenberg recalls telling her: 'This is not a big deal. We're not gonna let it be a big deal.' Then she directed Madonna to 'get back on her horse' and perform at the Live Aid concert before a worldwide television audience. The incident quickly shrank to the status of a footnote to the Madonna legend.
Since then, Pepsi has dropped her as a spokeswoman after viewing her 'Like a Prayer' video, the Vatican has exhorted Roman Catholics to boycott her concerts in Italy and the Canadian police have threatened to arrest her for lewdness. But under Ms Rosenberg's deft manoeuvring, Madonna has managed to bob back like a weighted penguin.
Ms Rosenberg prides herself on setting Madonna up with interviewers with whom there will be good chemistry. The publicist seems proudest of a widely syndicated interview published last year by the Advocate, the gay newspaper. She hand-picked the interviewer, Don Shewey, who queried the star about such matters as dildos and what she did with her old underwear. Ms Rosenberg, who was ensconced in an adjoining room crocheting 'like Madame Defarge', says she thought Madonna came across as 'funny and witty and brilliant and sparkling'. The Advocate interview appeared contemporaneously with - and as something of a corrective to - the film Truth or Dare. The publicist felt the movie made her client out to be an angry harridan. 'I thought she was much too heartless in the film,' Ms Rosenberg says. 'I was like, 'Oh, Madonna. How come you talk about your family like that]' Sometimes she listens. Sometimes she doesn't'
Michael Musto, a columnist for the Village Voice who covers the New York club scene, says: 'Liz has the easiest job in the world, and the hardest. On one hand, she can call up any magazine and get Madonna on the cover. On the other, she has to take calls from every crackpot around.'
When the tabloid papers circulated a rumour that Madonna was HIV-positive, she issued a statement, on Ms Rosenberg's recommendation, that the Aids stories were false, adding: 'If this is what I have to deal with for my involvement in fighting this epidemic, then so be it.' The rumours stopped.
In private Ms Rosenberg is a collector of kitsch and an avid reader of true-crime books, professing a particular fondness for 'family murders'. She lives in an apartment on the Upper East Side of Manhattan, something she has aspired to since she was a teenager. 'I always wanted to be Doris Day,' she says. 'You know, career girl, apartment overlooking The City.' A nursing student from Long Beach, Long Island, she was drawn to the music business by an enthusiasm for 'show tunes, Laura Nyro and Marvin Gaye'.
After secretarial jobs with various PR firms, Ms Rosenberg went to Warner Brothers. As a secretary and assistant to the director of publicity she was given latitude to spot and promote new talent. Among her early finds was Van Morrison. 'Nobody wanted to cover Van Morrison,' she recalls. 'I said: 'I'll do it.' I would have scrubbed his bathroom.'
During her ensuing 20 years at Warner Brothers, she has helped to mould the images of Fleetwood Mac, Rickie Lee Jones and Van Halen ('I personally distributed the backstage passes to the cutest girls in the audience'). But now she has attained celebrity in her own right, as Madonna's press agent.
'I count how many times I hear the 'M-word' mentioned in the course of my day,' she says with amused exasperation. 'My doorman asks me how Madonna is every morning. You know, my Aunt Pauline on her death bed asked: 'How's Madonna? Is the marriage gonna last?' I could get crazy, or I could just laugh about it.'
Two years ago, Ms Rosenberg married Phil Citron, a booking agent for Tom Jones and Julio Iglesias. Mr Citron is the one person in his wife's life who professes no interest in her celebrated client. 'I love him for that,' explains Ms Rosenberg, 'because obviously there are people who just see me as a person who will get them a little closer to Madonna.'
Meanwhile, Ms Rosenberg is gearing up to cope with the clamour over Erotica and Sex. The challenge for the publicist will be to position the album and book as works of art, not simply pornography. She describes the book in carefully chosen phrases such as 'beautifully done' and 'very, very funny'.
Ms Rosenberg knows there is a line that even her superstar client cannot cross. As the darling of the youth culture enters her mid-thirties, her ever-changing image will need to mature. Pop artistes who preen in lingerie, or nothing at all, tend to have a short shelf life.
No problem, says Ms Rosenberg, whose job, it seems, extends to putting the best possible spin on middle age. 'I'm sure that Madonna is going to do the forties like nobody - and be great at it. I just think she'll wear the most sophisticated, fabulous clothes and be worldly and a patron of the arts. I can't wait to see it.'
This article first appeared in the 'New York Times'.