Combine the pineapple juice and vanilla Set aside.
In a stand mixer, whisk together 3 1/2 cups flour, potato starch, yeast, brown sugar and salt.
Add in the pineapple juice mixture.
Let stand mixer go until dough has come together and easily coming off sides. Will be a little sticky.
Place dough on a lightly floured surface and sprinkle with some flour on top (enough for it to not stick to your hands). Form dough into a ball.
Once ball is formed, grease the same bowl mixed in and place the dough ball back into the bowl. *If you are oil free, then just make sure sides of bowl are floured, or use a silicone bowl to easily get it out
Cover with a towel or plastic wrap and let sit for 60-90 minutes in a warm, draft free place until doubled.
Once doubled, punch down dough and then pull off pieces into 16 even sizes. (We prefer to weigh the whole ball and then divide by 16 to ensure as even as possible).
With each piece, fold sides under and roll into balls.
Place each ball, seam side down, into a greased or parchment lined 9×13 baking pan.
Cover pan and let rise for another 30 minutes. *After this rise, you want the dough balls to be touching each other. If they are not touching, give them a little bit longer.
Preheat the oven to 375 degrees while rising this second time.
Using 1/3 cup of melted butter, brush each roll liberally.
Put into oven and bake for 15 minutes or until golden brown.
Remove from oven.