In the bowl of a stand mixer, mix together ¼ cup warm milk, 2 ¼ teaspoons instant yeast, and ½ cup granulated sugar. Allow the yeast mixture to sit for about 5 minutes or until it becomes frothy.
Once the yeast is ready, add ½ cup pineapple juice, ¼ cup softened unsalted butter, ½ teaspoon vanilla extract, 1 large egg, 3 ½ cups all-purpose flour, and ½ teaspoon salt. Using the dough hook attachment, mix on low speed to bring the dough together, about 5 minutes. You should have a sticky dough at this point, you may want to add more flour in ¼ cup increments with the mixer on medium-low speed.
Once all the ingredients have come together and you have the desired dough consistency, increase the mixer speed to a medium-high speed and knead for about 3-4 minutes to develop gluten. The dough will pull away from the sides of the bowl but still be pretty sticky. Continue to mix until the dough is smooth.
Transfer the dough to an oiled bowl and cover with plastic wrap that has been sprayed with non-stick cooking spray. Let the dough rise until doubled, about 2 hours.
Once the dough has doubled in size punch the dough down in the bowl and then split into 12 equal pieces and form into balls.
Grease a 13 x 9 x 2-inch pan and place the rolls in the pan. Cover with plastic wrap that has been sprayed with non-stick cooking spray. Allow the rolls to rise until doubled in size, about 1 hour.
When the rolls are almost doubled, preheat the oven to 350 degrees Fahrenheit. Combine 1 egg yolk with 2 tablespoons water and brush the egg wash over the top of the rolls.
Bake for 18-20 minutes, until golden brown. Serve warm or at room temperature.