Preheat the oven to 425 F degrees.
Place trimmed asparagus on a rimmed baking sheet and toss with 1 tablespoon of gremolata olive oil, fresh catch blend, salt and black pepper.
In a small bowl, stir together leeks, capers, remaining tablespoon of gremolata olive oil and a pinch of kosher salt. Sprinkle leek/caper mixture over the asparagus. Roast until the asparagus is tender and starting to brown, about 15 minutes.
While the asparagus roasts, make the mustard sauce: In a small bowl, whisk together dijon mustard, oregano white balsamic vinegar, capers and garlic. Slowly whisk in the gremolata olive oil until dressing is smooth and emulsified. Season with the fresh catch blend and a pinch of salt and pepper to taste.
Remove asparagus from the oven and transfer to a large platter. Sprinkle with fresh parsley and a squeeze of fresh lemon juice. You can either serve mustard sauce on the side or drizzle over the asparagus. Serve immediately or at room temperature.