In a large bowl, whisk together whole wheat flour, 1/2 cup of all-purpose flour, instant yeast, thyme, and salt.
Heat buttermilk until just warmed to about 100°F; it should feel comfortable to the touch on your inner wrist. Whisk in butter and honey, then whisk mixture into the dry ingredients until incorporated. Gradually add more flour until a cohesive dough is formed.
Turn dough onto a lightly floured board and knead, adding flour as needed, until dough is smooth and only slightly tacky to the touch.
Place dough in a greased bowl, cover, and let rise until doubled. Grease a 12-cup muffin tin.
Deflate dough and divide into 24 equal pieces. Roll each piece into a ball, then place two balls side by side into each cup of the muffin tin. Cover and let rise until puffy and just about doubled. Preheat oven to 375°F while the dough rises.
Bake rolls for 18-20 minutes, until golden brown.
Notes
If using active dry yeast, add it to the warm buttermilk and let rest 5 minutes before adding to the dry ingredients.