Well, I suppose it's difficult to formulate a proper response without knowing more details. Specifically, who initiated the ageplay/roleplay aspect into the relationship? If it was him, and you consented to explore new terrain, then it is more his responsibility to correct his image of you in his head. If you introduced the idea at the beginning, depending upon the initial response that it garnered from your partner, then it may be something that you both need to sit down and really hash out in an adult discussion.
Granted it lies in both of your hands to make it work, but whomever presented the game to the other might take on just a bit more of the brunt of responsibility for sorting it out at this point. I say this due to my own thoughts on establishing a roleplaying relationship and the potential problems that might ensue. At what point do you fall out of the role and stop pretending? Once someone adopts a headspace, whether top or bottom, that switch gets set inside one's head. Granted the degree can fluctuate depending upon the circumstance, but submissive is submissive and dominant is, well, you get the point.
What factors does your play hinge on? Does your play last for hours, days, weeks at a time? Or is it something that is over once you have consummated the experience? If you are over and done with after having a good ol' fashioned romp then it should be easier to shake, while playing for wildly extended periods of time further ingrains the idea of the role.
There is also the question of 'how' you play. Without attempting to get you to dredge out personal and/or graphic details of your personal sex life, you should-for yourself-consider to what degree your playing takes. Is it light and topical or involved heavily in the psychology of it. The deeper you delve into the psyche, again, the more ingrained the characterization becomes.
There are a lot of factors to consider before really determining how to approach the problem at hand. And even after all the evidence has been collected, truly no one but yourself can decide an outcome that will work for you except yourself. You will never remove a weed unless you attack at the roots.