If Rolf had been drinking something, he'd have snorted out the beverage through his nose at the 'butter up with the vagina' remark. His eyes caught Rose's though, and he followed her lead, eyes crinkling up at the corners slightly in mirth. "Oh yes, my darling. Only for your perky boobs," he lied (badly but dramatically) in a perky voice. He ogled them for good measure. He flopped down partly across Dennis as well. "Oh he has the prettiest eyes," he agreed, laughing.
Rolf put whatever reference Dennis has just made into the 'it must be from the Muggle world' box in his head. He'd figure it out later. While he had passing familiarity with some facets of the Muggle world, there was very much he didn't know about it.
"Oooooh I love the Caribbean," he said, echoing Rose. "Let me get a shop-sitter and I'm totally in on that."