In a large bowl, toss the mixed vegetables with olive oil, salt, and black pepper.
Spread the vegetables on a baking sheet in a single layer.
Roast in the oven for 20-25 minutes, or until tender and slightly caramelized.
While the vegetables are roasting, prepare the vinaigrette by whisking together Dijon mustard, apple cider vinegar, honey, and olive oil in a small bowl.
Once the vegetables are done, let them cool slightly.
In a large serving bowl, combine the roasted vegetables, red onion, cherry tomatoes, and feta cheese.
Drizzle the Dijon vinaigrette over the salad and toss gently to combine.
Serve warm or at room temperature.
Notes
Feel free to use any seasonal vegetables you have on hand.
This salad can be made ahead of time; just add the vinaigrette before serving.