Preheat oven to 475°.
Line a rimmed baking pan with aluminum foil. In a medium bowl, toss asparagus with olive oil and salt and pepper, to taste. Arrange asparagus on pan in an even layer and roast 10 to 15 minutes (depending on size) or until cooked through – give the pan a shake after 5 minutes in oven to move asparagus around. Asparagus can be served either warm or at room temperature with black olive aioli served in a separate bowl.
Black Olive Aioli
In the bowl of a food processor, combine garlic, yolks, lemon juice, mustard, and scallions. Process until blended. With machine running, slowly pour in olive oil, beginning with a few droplets and increasing to a thin, steady stream as the mixture emulsifies, until all of the oil is absorbed and the mixture is a thick mayonnaise consistency. Fold in olives and season with salt and pepper to taste. If the mixture seems too thick, thin it with a few teaspoons water; this will make it creamier.