In a microwave safe bowl, mix together brown sugar, pineapple juice, melted butter, and buttermilk. Microwave the mixture in 30 second increments until it reaches 110°. If you do not have a thermometer, use a finger to dab the mixture on the inside of your wrist. If it feels warm it is ready.
Pour the mixture into the bowl of a stand mixture with a dough hook attachment. Add in yeast packet and whisk lightly with a fork to incorporate. Wait about 5 minutes for the yeast to bloom, or get foamy.
With the mixer on a low speed, add in the crushed pineapple, beaten egg, and salt. Once incorporated, slowly add in the flour, one cup at a time.
Once all of the flour has been added, increase the mixer speed to medium, until the dough forms a ball and pulls away from the sides of the bowl. The dough should be soft but not sticky. If it is too sticky, add about a tablespoon of flour in at a time, up to ⅓ cup, until no longer sticky.
Brush a large bowl with melted butter. Form dough into a ball and place it in a bowl. Brush with a little bit more butter. Cover the dough with plastic wrap or a warm towel and store in a warm dry place until the dough has doubled in size, about 1½ hours.
Once the dough has doubled, punch the dough down and place it on a lightly floured surface.
Cut the dough in half, and then each piece in half again, forming 4 equal pieces. Cut each of the four pieces in half two times, to form 16 total pieces.
Take each piece and form a ball, gently pulling the top of the dough down and pinching it at the bottom so it is smooth on top. Place all 16 balls in a lightly greased 9x13 inch baking dish. Cover again with a warm towel or plastic wrap until the dough doubles again in size, another 1½ hours.
Preheat the oven to 375°. Brush the rolls with butter and bake for 25-30 minutes until the rolls are golden brown.
Brush with more butter and allow to cool in the pan for 10 minutes. Serve immediately or store in an airtight container.