Preheat the oven to 425 degrees F.
Divide and toss the asparagus with the olive oil, salt, and pepper, and arrange in a single layer on 2 to 3 separate large rimmed baking sheets.
Place in the oven and roast until the spears are tender and the tips are turning golden and slightly charred, 10 to 12 minutes.
Prepare the vinaigrette while the asparagus is roasting. To a bowl, add the Dijon mustard, vinegar, salt, and pepper. Whisk in the olive oil to emulsify. Taste for seasoning and adjust, if necessary.
Remove the asparagus from the oven and place on a serving platter. Drizzle with the vinaigrette and sprinkle with the feta cheese. Serve warm or at room temperature.