Preheat oven to 400 degrees F.
Place asparagus, onion, cherry tomatoes, and red bell pepper on a baking sheet.
Add avocado oil and toss together to coat.
Lay the vegetables in an even layer and roast for 20 minutes, stirring them halfway through.
While the vegetables are roasting, combine all ingredients for the dressing in a mason jar.
Screw on the lid and shake vigorously until emulsified. Set aside.
Once the vegetables are done cooking, transfer them to a large mixing bowl.
Add kalamata olives and cucumbers.
Pour the dressing over the vegetables and toss together until combined. Add more salt if needed.
Serve at room temperature.