Carefully cut the rough ends off of bases of the asparagus spears, removing about 1 inch.
Spread the asparagus on a parchment-lined baking sheet. (Asparagus can be touching, but should not overlap; if needed, use a full sheet pan or two half sheets.)
Pour the olive oil over the asparagus, coating evenly.
Squeeze lemon juice over the asparagus, coating evenly.
Sprinkle the asparagus evenly with salt and pepper, and roll the spears around to coat each side.
Put the baking sheet in the preheated oven and roast the asparagus for 20 minutes, or until tender.