Place a sturdy pot with a tight-fitting lid over medium heat. Add the oil to the pan (use enough to coat the bottom), along with the rosemary. Allow the mixture to sit on the heat for about a minute, then raise the heat to medium-high. Add the popcorn and place the lid on the pan. Shake the pan as the popcorn pops, until you hear it start to slow down in frequency of pops. When you hear 3 to 4 seconds between pops, take off the heat, and add salt and garlic powder to taste. Enjoy!