"I love when he dresses up in his old Navy uniform. I didn't know him then, so it makes things different, and men-in-uniform really turn me on."
"My husband has a foot fetish. When I wear stockings and heels, he loses his mind."
"Maybe I'm all screwed up, but I like playing the naughty school girl (with pigtails!), and he's the teacher who punishes me for getting my homework wrong."

Taking on a different persona can be freeing and allow for actions and thoughts to play out that you as a "real person" wouldn't be able to follow-through with. By putting on a costume or assuming a different role, you can kill off inhibitions and self-conscious insecurities that would prevent pleasure.

Bottom line: Assuming a new role can not only be fun, it can eliminate relationship dynamics that might stifle sexual freedom.