Combine the chopped root vegetables and red onion in a large bowl. Drizzle with olive oil, thyme, salt, and pepper. Toss to coat evenly.
Spread the seasoned vegetables in a single layer on a large baking sheet. Roast for 25 to 30 minutes, stirring halfway through, until tender and slightly caramelized.
While the vegetables roast, cook the lentils. Combine the rinsed lentils and vegetable broth in a medium saucepan. Bring to a boil, then reduce heat to low, cover, and simmer for 20 to 25 minutes, or until the lentils are tender but not mushy. Drain any excess liquid.
Prepare the dressing. In a small bowl, whisk together the red wine vinegar, Dijon mustard, and maple syrup until smooth.
In a large bowl, combine the cooked lentils and the roasted vegetables.
Pour the dressing over the lentil and vegetable mixture. Toss gently to combine everything.
Stir in the fresh parsley. Serve warm or chill for later use as a healthy make ahead option.
Notes
For best results in meal prep, store the salad undressed for up to 4 days. Add the dressing just before serving.
Add 1 cup of cooked quinoa or farro to this recipe to make it a more substantial hearty grain bowl.
This plant-based protein salad keeps well in the refrigerator for lunches all week.