I actually liked roasting the rice and the millet. And so far it is the only gluten free beer I've made that has held a head worth a darn. I think the grains may have had something to do with that but I'm not a beer recipe expert, I'm just going with my limited experience.
I certainly like where you are going with that recipe. I think when I do it again I'm going to do more of the roasted rice, cut down on the chocolate like you have done, add a pound of honey at the end, maybe a little cardamom (I put some in a wheat wine for me and if I use it again I'll add it to the secondary and not at the end of the boil like I did with my wheat wine because it is overpowering). I used some coffee last time and I'm going to ditch that entirely. And I think I might go with two bananas in the boil like I did with this IPA. I'm also trying to figure out how to make it darker. I want it nearly black. I've seen some people using tea so I wonder about some black tea we have sitting around here that never gets used.