Preheat the oven to 450 degrees F.
On a baking sheet, toss the asparagus with 1 tablespoon of the oil and the salt and pepper. Arrange in a single layer and roast until the asparagus is tender, 10 to 13 minutes.
Meanwhile, in a skillet over medium-high heat, cook the bacon until crisp, 3 to 4 minutes. Remove to a paper-towel-lined plate to drain, reserving 3 tablespoons of the bacon drippings.
In a medium bowl, whisk the bacon drippings, mustard, vinegar, honey and the remaining 2 tablespoons oil until combined.
To assemble: Plate the asparagus. Sprinkle with bacon and feta, and drizzle with Dijon dressing. Finish with flaky sea salt. Serve warm.