In a large mixing bowl or stand mixer, combine the water, buttermilk, molasses, honey, and softened butter.
Add the fresh-milled flour, instant yeast, salt, and cocoa powder. Mix until the dough just comes together—it will look soft and loose.
Cover and let the dough rest for 25 minutes (autolyse).
Knead for 8–10 minutes, until smooth and elastic. Dough will remain slightly tacky; use oiled hands to handle it.
Place dough in a lightly greased bowl. Cover and let rise until doubled, about 1 hour.
Turn dough onto a lightly oiled surface and divide into 16 rolls or slider buns. Shape tightly.
Let rise again until doubled, about 45 minutes. Use the poke test to check readiness.
Bake rolls at 350°F for 18–22 minutes, or until the centers reach 190–195°F.
Cool rolls on their sides for 15–20 minutes, then transfer to a rack to cool completely.