Roast the vegetables: Heat oven to 450 °F (232 °C). On a baking sheet, toss potatoes and onions with oil, thyme, and salt and pepper. Arrange all potatoes cut sides down and roast both sheets, rotating positions of sheets halfway through, until golden brown and tender, 25 to 30 minutes.
Lay the bacon in a skillet and place over medium heat. Cook on both sides until golden brown and crispy. Set aside on paper towels to drain excess grease.
Discard thyme from the roasted vegetables and transfer half of them to a large pot. Add chicken broth and bring to a boil. Using an immersion blender (or standard blender), puree until smooth.
Add the corn (thawed) and remaining roasted vegetables to the pot and bring to a simmer. Stir in heavy cream, fresh lemon juice, bacon, and scallions, and season with salt and pepper to taste.
Warm the rolls in the oven for 2 to 3 minutes. Then spread the butter inside.
Mix all the ingredients for the Shirley temple. Serve over ice if desired.
Portion the soup and garnish with parsley. Enjoy with rolls and Shirley temple.