Give him a list of naughty role-playing options to choose from, like "Let's try something fun today! Since you've been a darling lately, I'll let you make the choice. Would you like me to (A) dress up as a schoolgirl or (B) play your secretary at work or (C) try a little S&M?" Since you're the one who proposed the ideas, he knows he'll be able to choose whatever he prefers from the menu without you freaking out.
7. Do up a not-list
Rather than revealing your steamy imaginings, it may feel safer for both of you to share what you're not into. Write down a list of things that you wouldn't want to explore or which turn you off, then exchange this list. You'll be able to narrow down the possibilities and take it from there.