Preheat oven to 450 degrees.
While the beets are roasting, scatter the grapes on a nonstick foil lined sheet tray and drizzle with olive oil. Roast for 20-25 mins until softened and just beginning to burst.
Allow the beets to cool and then peel them with a paring knife. You can use gloves or hold with a paper towel, being careful not to stain everything with the beet juice.
Whisk the mustard, honey, vinegar and salt and pepper together until blended.