When people roleplay they tend to go for the clichés; a pretty French maid for you and a demanding teacher for me, a school girl and all that jazz. The thing is that you don't need a lot of fancy costumes to roleplay. Roleplaying is all in the mind, it has to be or else it wouldn't work. Changing into a costume isn't going to convince anyone that they have a genuine Fortune 500 CEO in front of them (unless you actually are one), so some imagination is needed.
You're also going to need to make sure that (like with all fetishes) that you ease your way into this one. Maybe you've always wanted to dress like a woman and you think your affair partner would be into it. Well unless you want to be slapped with a restraining order, we wouldn't suggest surprising her with it. Human beings are not meant to process changes that quickly. Our routines protect us and more than that, they keep us happy and help us to feel safe.
You also don't need to spend much in the way of money on elaborate costumes. There are plenty of ways that you and your affair partner can have sex roleplay without breaking the bank. All you need is a few props and a good imagination for you to be in a ton of different scenarios.
One scenario that is easy to do and won't cost you much in preparation or money is to pretend that you’re meeting your affair partner for the first time in a bar. Having sex with a complete stranger when you know in the back of your mind that you can trust them is an uplifting experience and we would suggest it to anyone who wanted to roleplay without getting into the truly fantastical or the porn elements.
You could also play bartender at one of your houses and be that stoic, somewhat broody guy that women dream of in a one night stand. The best part about this is that everyone wins. You get to have her tell you about her day and she, if she gets tipsy enough, would probably give you the best bartending tip you’ve ever had in your life.
One of the things that you need to keep in mind with roleplay is that you both are going to need to get into the right mindset. Otherwise it’s just sex with silly costumes that you both will never want to wear again. It’s not the costumes or the props that matter with roleplay, but your imagination.
If you can imagine that the bikini your affair partner is wearing is a Princess Leia slave bikini and that you’re the dashing Han Solo, then you’re going to have a lot of fun. If you don’t have the imagination to stretch that far then just keep it simple. It’s tempting to go all out and spend money on this particular fetish, but you need to be able to keep in character.
If you can’t, then you’re going to get disappointed.
As for how to ask your affair partner to roleplay with you, you can ease them into it gently by asking about their fetishes and then coming up with roleplay scenarios to accompany them. Do they like massages? Create a scenario where you’re a professional masseuse who can’t keep their hands off of the client even though they know that they shouldn’t be doing this.
Are they into police officers? Then pretend you’re an undercover cop and arrest her under suspicion of whatever crime you think would apply. Try to stay away from stupid one liners like “You’re under arrest for suspicion of being too sexy.” No one is going to buy that and these little things that remind your affair partner that you’re not actually who you say you are will end up detracting from the scene.
Be safe and have fun! Keeping it simple is going to help your roleplay a lot until you and your affair partner get used to roleplaying with each other.