Preheat the oven to 375°. Place a large piece of heavy duty aluminum foil on a baking sheet. In the middle of the foil, place the beets, 2 tablespoons of oil and the garlic and thyme; season well with salt and pepper. Crimp all four corners of the foil to make a air-tight package and place the baking tray in the oven. Roast for about 1 1/2 hours (this will vary depending on the size of your beets, small ones could be done in as little as 45 minutes so check every so often), until the beets are tender and the flesh of the beet is pierced easily with a knife. Allow beets to cool and then peel the skin using the abrasion of a paper towel. Cut them into slices and set aside.
Meanwhile, spread the hazelnuts on a baking sheet and bake for about 12 minutes, until fragrant. Transfer the nuts to a kitchen towel and let cool slightly, then rub them together in the towel to remove the skins. Coarsely chop the nuts.
In a medium bowl, whisk the lemon juice with the shallot and mustard and let stand for 10 minutes. Add the honey and gradually whisk in the remaining 1/2 cup of olive oil and season the dressing with salt and pepper.
In a large bowl, toss the kale with just enough dressing to coat lightly, Arrange on a platter. In the same bowl, toss the beets with 3-4 tablespoons of the dressing and season with salt and pepper. Arrange the beets on the platter, on tp of the greens and sprinkle the hazelnuts on top. Scatter the goat cheese and scallions over the salad and serve, with the additional dressing on the side.
MAKE AHEAD The roasted beets can be refrigerated for up to 3 days. Bring to room temperature before proceeding. The dressing can be refrigerated for up to 2 days.