Mix golden flax meal and water in a small bowl until well combined. Let it rest for 5 - 10 minutes to thicken.
In a microwave-safe bowl combine the buttermilk and butter. Microwave in 20-second increments until the mixture is warmed (110°F approx.,).
In the bowl of your stand mixer fitted with the paddle attachment add in the flax meal mixture, buttermilk mixture, pineapple juice, vanilla, sugar, and yeast. Stir on low until combined.
Add in 2 cups of flour, potato flour, and salt and mix on medium speed for 1 minute. Gradually add in 2 1/2 more cups of flour, until a soft dough form. Add a little bit more flour, 1 tablespoon at the time, if the dough is too sticky.
Replace the paddle attachment with a dough hook and knead on medium speed until the dough forms a soft, smooth ball, about 5 – 8 minutes.
Lightly spray a clean bowl cooking spray and place the dough in the bowl. Cover with plastic wrap or a clean kitchen towel. Let rise in a warm place until puffy and doubled in size, about 1-2 hours.
Spray a 13x9-inch baking pan with cooking spray. Set aside.
Gently deflate the dough and divide into 15 equal portions (about 75 gr each). Form the dough into balls and place in the prepared pan. Cover again with the towel and allow the dough to rise for 30 minutes.
Meanwhile, position one of the oven racks into the center of the oven. Preheat the oven to 375º F (190º C).
Mix the eggless egg wash ingredients in a small bowl.
Once the rolls have risen, lightly brush the tops of the rolls with the eggless egg wash.
Bake them for about 15 - 20 minutes or until golden brown. Brush them with melted butter immediately when they come out of the oven.
Serve warm or at room temperature.