In a small bowl, mix yeast and ½ teaspoon sugar with warm water. Let stand until bubbly (about 10 minutes). The mixture should look foamy or bubbly before you continue. If it does not, the yeast may be inactive and it is best to start again.
In a large bowl, stir together 1 cup warm milk, ½ cup oil, ½ cup sugar, and 1 teaspoon salt with a wooden spoon.
Add 1 cup flour and mix well. Add 2 eggs and mix vigorously until smooth, then stir in the yeast mixture.
Gradually add the remaining flour, mixing just until the dough is smooth, soft, and slightly sticky. You may not need the full 5 cups, so stop adding flour once the dough reaches the right consistency.
Transfer the dough to a lightly greased large bowl. Cover the bowl with a tea towel and let rise in a warm, draft-free spot until doubled in size. Depending on the temperature of your kitchen, this may take a few hours.
Once the dough has doubled in size, punch it down and divide it in half. On a floured surface, roll each piece out into a 12-inch circle. The dough circles should be about ⅜ inch thick.
Brush the dough with melted butter, then cut each circle into 12 even wedges, like a pizza. Starting at the wide end of each triangle, roll the dough toward the pointed tip to form a crescent. Place each roll seam-side down in the greased baking pan so it stays rolled while baking (we use an 11x15 metal pan and do 3 across and 8 rows down).
Cover again with a tea towel and let rise until the shaped rolls look puffy and have doubled in size, about 1 to 2 hours.
When ready to bake, preheat the oven to 375 degrees F.
Bake for 16 to 20 minutes, until the rolls are lightly golden brown. Check one of the center rolls for doneness by gently pressing the top. It should spring back when touched. If the tops are browning too quickly before the centers are done, loosely tent the pan with foil and continue baking. Brush the warm rolls with melted salted butter and serve.