Preheat your oven to 400°F. Meanwhile, peel the beets. I leave the peels on the sweet potatoes, but you can peel those too if preferred, then cut everything into 1-inch cubes.
In two separate bowls, toss the sweet potatoes and beets with 1 tbsp olive oil each.
Roast the beets first. Transfer the beets to a sheet pan (you can use one large 14x20 sheet pan for both veggies or two smaller pans- one for beets and one for sweets), and roast for 20 minutes.
After the beets have roasted for 20 minutes, slide the sweet potatoes into the oven, sprinkle the beets and sweet potatoes with kosher salt, and roast everything for another 25 minutes.
While potatoes are cooking, spray a medium skillet with olive oil and heat to medium heat. Sauté pancetta and onion until the onion is soft and pancetta starts turning a little golden brown and crispy. Transfer to a paper-towel-lined plate and set aside to cool.
When the beets and potatoes are done, cool to room temperature, then assemble your salad.
Place greens in a large bowl, top with the beet and sweet potatoes, pancetta mixture, goat cheese, and pecans.
Right before serving, drizzle with the desired amount of light or regular balsamic vinaigrette and toss to mix.