Position rack in top third of oven and preheat to 425°F. Line a rimmed baking sheet or two with foil and spray or oil it.
In a large microwave-safe bowl, add diced potatoes and two or three tablespoons water. Cover tightly with plastic wrap and microwave for five minutes. Remove, carefully open the wrap, stir, replace wrap and microwave for two to three more minutes until potatoes are partially cooked and the edges look a little soft and “gummy.” Drain.
Place Potatoes and Brussels Sprouts on prepared tray. Drizzle with olive, salt and pepper, and thyme to taste. Toss. Spread into a single layer. If vegetables won’t fit on a single tray in a single layer, use two.
Place in oven and bake until the potatoes and Brussels sprouts have started picking up color, about 20 minutes. Stir and continue to roast until vegetables are cooked to your liking, tender and browned in spots, 10 to 15 minutes longer. If using two trays, rotate from top and bottom and front to back for even roasting. If vegetables are finished cooking and not caramelized to your liking, turn on the broiler for a minute or two.
Remove from oven and drizzle with White Balsamic & Honey Vinaigrette, taste for seasoning, and add more salt or pepper as needed. Toss with nuts, dried cherries, dried cranberries, or pomegranate seeds.
Serve warm or at room temperature. Can be made ahead a day and refrigerated. Let stand at room temperature for about 30 minutes and rewarm in a 350°F oven about 15 minutes.
White Balsamic Vinaigrette:
Whisk ingredients together. Taste and adjust by adding more honey, vinegar, or salt and pepper as desired.