Dynamic Missing in Relationship

I am currently engaged to a man I love and have so much fun with. He is my best friend and a great partner. I'm struggling right now though with our "roles" in the relationship. We keep things on a pretty level playing ground and sexually speaking we have been trying new things.

In past relationships I have always gone for more strong, dominant men. My SO however, is smaller than me and not even as strong. I want him to take on a more masculine/dominant role in our relationship but I have no idea how to tell him with hurting his feelings or making him insecure. He knows/has seen some of the men I've dated in the past and have often asked me if he is "man enough" for me. And he is so much more than I could have ever hoped for in a partner...I just wish he would take a little more control in and out of the bedroom.