Preheat oven to 400˚F. Place several thickness of paper toweling on a work surface near the oven. Line a sheet pan with foil for easy cleanup.
Arrange bacon strips on foil so they aren’t overlapping. Bake for 10 minutes or until strips are beginning to turn golden but are still soft. Remove the pan from the oven and transfer bacon to paper towels to drain.
While bacon is baking, bring a large pot of water to a boil. Add beans, cover and cook for 1 minute. Place a strainer in the sink and drain beans. Immediate rinse beans with cold water for 1 full minute. Drain well and then transfer beans to a clean kitchen towel. Pat with the towel to remove as much water as possible.
Place beans in a medium-size bowl. Combine olive oil and garlic salt. Drizzle oil over the beans and toss to coat.
Arrange beans in 12 bundles of 10-12 beans. Place one bacon strip on a work surface. Place a bundle of beans on one end of the bacon strip. Roll bacon around the bundle and secure with a toothpick. Repeat with remaining bacon and bundles of beans. Arrange beans on a sheet pan lined with clean foil.
Combine brown sugar and rosemary in a small bowl and stir well. Sprinkle one teaspoon of the brown sugar mixture over each bean/bacon bundle.
Bake bundles for 15-20 minutes at 400˚F or until bacon is golden brown and beans are tender. Remove from oven and serve warm. Remove toothpicks and garnish with more finely chopped fresh rosemary, if desired.