Pre-heat oven to 400F degrees.
In a small bowl mix in the melted butter, capers, juice from a half-lemon, salt + pepper and set aside.
Wash and trim the asparagus, then arrange in a sheet pan. Pour the lemon butter sauce over the asparagus and roast for 15 mins.
As for the radishes you can add the thin slices on top of the asparagus and roast for an additional 2 minutes or leave them raw. I personally like the crunchiness of raw radishes.
Garnish with fresh dill and serve immediately.