Preheat your oven to 400°F (200°C).
Place trimmed asparagus and halved radishes on a baking sheet. Drizzle with olive oil and season with salt and pepper. Toss to coat.
Roast the vegetables in the preheated oven for about 20–25 minutes, turning once halfway through.
In a bowl, whisk together whole grain mustard, Dijon mustard, apple cider vinegar, minced garlic, olive oil, and honey if using.
Taste the vinaigrette and season with salt and pepper to your preference.
Arrange the roasted asparagus and radishes on a platter and drizzle with the mustard vinaigrette before serving.