Being a member you have a right to ask any question.
You are talking about role play with wife and in your 2nd post you wrote:
"Playing like strangers with wife or as brother sister etc" Do you deny your words?
It shows the fantasies you have in your mind, what you wish to do
Would you mind explaining what do you mean by brother sister? Do not you count it in "incest category"?
You said in your 3rd post "it is common thing among couples to have a role play to spice up their sex life" means you already know about it than, why you need a fatwa on it?
There are many things which are prohibited in religion but people are practicing them without any hesitation.