Arne,
If you're aiming for the highly aerated crumb structure typical of teglia romana, I would first make a base dough using only wheat flour and then, after the gluten is well-developed, add the corn component in the form of polenta rather than dry cornmeal. A series of "stretch and folds" should help incorporate the ingredients. I would make the polenta using a finely-milled cornmeal to avoid any grittiness in the finished product. Another tip would be to make the base dough entirely of semola rimacinata in order to bolster the yellow colour typical of many cornbreads.
Rolls