Roasted Beet Salad with Oranges and Creamy Goat Cheese Dressing

1 pound small golden and red beets, scrubbed 2 tablespoons olive oil, plus more for drizzling Kosher salt and black pepper 3/4 cup plus 2 tablespoons orange juice 1 teaspoon sugar 4 ounces goat cheese, room temperature 2 tablespoons champagne vinegar 1 tablespoon heavy cream 2 medium oranges 8 ounces baby arugula 1/2 medium red onion, thinly sliced