Preheat the oven to 400 degrees F (200 degrees C) and line a large baking sheet with parchment paper or a silicone mat.
In a large bowl, toss the cubed sweet potatoes with 2 tablespoons of olive oil, ½ teaspoon of salt, and ½ teaspoon of black pepper. Spread them on one half of the baking sheet.
In the same bowl, toss the cubed beets with the remaining 2 tablespoons of olive oil, ½ teaspoon of salt, and ½ teaspoon of black pepper. Spread them on the other half of the baking sheet.
Roast for about 30 minutes or until the beets are tender. Check the sweet potatoes at the 20–25 minute mark and remove them early if they begin to burn, as they cook faster than beets.
Meanwhile, place the thinly sliced red onions in a large salad bowl. Add the lemon juice and a pinch of salt, and mix well. Set aside to marinate while the vegetables roast.
Once the beets and sweet potatoes are done, remove from the oven and allow them to cool slightly on a wire rack.
To the bowl with the marinated onions, add the balsamic vinegar, apple cider vinegar, agave or maple syrup, and a pinch of black pepper. Slowly whisk in the dressing and set aside.
Add the arugula to the bowl and toss well to coat with the dressing. Add the roasted vegetables and pecans, then toss again gently to combine.
Top with vegan feta and serve immediately.
Notes
Cut the vegetables evenly: So they roast evenly. It’s a good idea to cut the beets slightly smaller than the potato, as they take longer to cook.
Don’t overcrowd the vegetables: Otherwise, they’ll steam rather than becoming caramelized with crisp edges.
The cooking time may vary: Based on the size of the veggies.
Let the veg cool: To avoid wilting the leafy greens.