In a small saucepan, stir pineapple juice, milk, sugar, and 2 tablespoons butter together. Heat over low heat just until butter melts and sugar dissolves. Cool to about 100-105 F.
Pour the milk mixture into the bowl of a stand mixer.
Add the yeast, and let stand for 5-10 minutes, or until yeast is foamy.
Mix in egg and vanilla until combined.
Add 2 cups flour and salt to yeast mixture. Using a dough hook, mix on low speed for about 1 minute.
With the mixer still going, add remaining flour, 1/4 cup at a time. Mix about 1 ½ minutes, or until dough starts to clean the sides of the bowl.
Knead on low speed for about 2 more minutes, or until dough is smooth and elastic – the dough will still be slightly sticky to the touch.
Place dough in a greased bowl, turning it to grease the top. Cover the dough with a clean, dry dish towel.
Let it rise in a warm place, free from draft, for about 15 minutes.
Turn the dough onto a lightly floured surface, and divide into 12 pieces for rolls or 7 pieces for buns.
Form each piece into a ball and place on greased pan. I use a quarter sheet pan.
Cover the pan with the dish towel, and let the dough rise for about 20 minutes.
Melt remaining 2 tablespoons butter. Set aside
Bake at 400ºF for about 8-12 minutes, or until the rolls are golden brown.