Place the beets in a single layer in a large roasting pan (it may take two pans; do not overcrowd). Drizzle with the olive oil. Give the pan a vigorous shake to move the beets and cover them with the oil. Sprinkle with salt, and cover the pan with aluminum foil. Roast for 60-90 minutes, depending on the size of the beets, until tender. Remove from oven and allow the beets to cool just enough for you to be able to peel them using a few paper towels.
Cut them into a 1/2″ dice and place in a large bowl. Toss in the julienned red onions and set aside at room temperature while you make the dressing.
Combine the vinegar, lemon juice and sea salt in a small bowl and stir. Slowly drizzle the olive oil into the mixture, whisking as you pour to combine.
Drizzle the dressing over the beets and onions and toss with tongs to combine. Check the seasoning. Cover the bowl and marinate overnight in the refrigerator.
For Garnish: Place a large, heavy bottomed skillet over low heat. Add the oil, pistachios and salt. Cook the pistachios, stirring often until crisp and very lightly browned, approx 8-10 minutes.
To Assemble: Bring beets to room temperature in order for the olive oil to liquefy again. Toss the mixture one more time, check for seasoning and serve by dividing the beets among 8 plates.
Garnish each plate with 1/2 ounce of pistachios and 1 ounce of goat cheese.
If preferred, you can add the pistachios and chevre to the salad bowl and serve family-style.