In a small bowl, stir together yeast, cane sugar, and warm water; let mixture stand in a warm place until yeast begins to foam, about five minutes.
Meanwhile, combine whole wheat flour, chopped rosemary and salt in the bowl of a stand mixer fitted with the dough hook. Make a well in the center.
Whisk yeast mixture with a fork until dissolved. Add buttermilk; stir in egg. Pour into the flour well.
With the mixer on low, combine flour and liquid until just combined. Turn off mixer and allow to sit for 10 minutes for the wheat to absorb the liquid.
Scrape down the sides of the mixer. With the mixer on low, add butter, one tablespoon at a time, until it is all absorbed.
Knead dough on low for five minutes, scraping down the mixer as needed. Dough will come together to be a smooth, elastic mass. It will be sticky, but do not add more flour.
Grease a medium bowl with olive oil and place bread dough in the bottom. Cover loosely with plastic wrap or a tea towel and allow to rise in a warm place for 1 hour.
Place your jam jars on a cookie sheet and prepare by oiling generously with olive oil and sprinkling the bottoms with cornmeal.
Turn dough onto a oiled counter and divide into ten or twelve pieces. Shape dough into round balls, as demonstrated in the short video (also available on Vimeo), and place into prepared jam jars. Cover with a clean towel and allow to rise for one hour.
Preheat oven to 400°F. Brush the tops of the rolls with melted butter and snip tops with scissors. Place rosemary sprig in the center of the snipped area and sprinkle tops with sea salt.
Place in a hot oven and bake for 22 minutes. Remove from oven and allow to cool slightly. Serve warm.