Peel, halve and slice beets, creating 1/4-inch half-moons.
Add to salted, boiling water; cook till fork-tender (do not over cook). Add trimmed asparagus to the water for 2 minutes, strain and cool.
Slice red onion into 1/2-inch rings.
Toss beets with olive oil and salt and pepper. Combine with onion and roast in a 400 degree F oven for 15 minutes.
Brush slices of baguette with olive oil and top with goat cheese. Toast at 400 degrees F until golden brown.
Arrange mesclun in the center of the plate with a small pile of beets perched atop. Place a small bunch of asparagus on top of the beets, drizzle with dressing, and garnish with the goat cheese crouton.