Pour pineapple juice into a microwave-safe bowl. Heat for 90 seconds in the microwave.
Slice butter into small squares. Add butter and sugar to pineapple juice. Stir. Allow hot pineapple juice to sit until it cools to around 110 degrees (warm, not HOT), and the butter is mostly melted.
While the pineapple juice cools, combine water and yeast in a small bowl. Let it sit until it puffs up.
Pour pineapple juice mixture, water and yeast mixture, and egg into a stand mixer bowl. Mix on low using the paddle attachment. Add salt and flour, 1 cup at a time, and mix on low.Note: this is a SOFT dough and might be sticky. That's totally normal. Swap the paddle attachment out for the dough hook and mix in low for an additional two minutes, or until the dough starts to pull away from the sides. Add 1/4 cup of flour, if necessary (see notes at the bottom of the recipe about flour).
Scrape the sides of the bowl with a rubber spatula and form the dough into a ball in the center of the bowl (see photo above).Note: If you do not have a stand mixer you can make this dough by hand using a Danish dough whisk in a large mixing bowl. Mix the ingredients together, then knead on a lightly floured surface for a few minutes until it comes together. Loosely cover the bowl with plastic and let rise in a warm location for 90 minutes.
Transfer dough to a lightly floured surface and form into a ball. Divide the dough in half and then in half again (you will have 4 portions of dough). Form 6 balls from each portion of dough, for 24 rolls.
Place rolls in two greased 9"x 13" baking pans (12 rolls per pan). Cover loosely with plastic and let rise in a warm place until doubled, about an hour.
Preheat oven to 350 degrees. Bake rolls for 20 minutes or until tops are golden.
Brush hot rolls with melted butter.