The stylist to the stars says the singer-and-actress is quite "boring" with her fashion choices and wants to update her whole wardrobe.
He said: "Her look is boring. I would change her up constantly because she is not diverse enough. I would give her a Hitchcock heroine look, a 50s look, and some serious 60s hippie look."
However, while he's not a fan of her look, Robert believes she has The Cut right with her clothes.
He told UsMagazine.com: "Tight always looks better than loose when you are being photographed and when you are on television. You are on the side of tight no matter what."
Jessica Simpson - whose weight has fluctuated over the years - recently revealed how she loves clothes which give her a nipped-in waist and show off her womanly curves.
She said: "I'm a huge Jean Paul Gaultier fan. His pieces make my waist look good. Yes, they're an investment, but I'll have them when I'm old and grey."