Not really a pilaf, you cook the vegetables and the grain separately and combine them just before serving.

Coat 1 large or two small baking sheets lightly with olive oil.

Trim 1 bunch of asparagus and cut into half-inch pieces.

Scrub 3 beets and cut into small dice about the same size.

Trim 2-3 spring onions and chop.

Lay the vegetables out in a single layer on the sheet(s).  Keep the beets separate, as they might take longer to cook and tend to bleed.
Sprinkle salt and pepper over all.

Bake at 400 degrees, until the asparagus is light browned, the onions are nicely browned, and the beets are tender but not soft.  Deglaze the pan with the juice of 1 lemon or orange.

Meanwhile, cook 2 C. quinoa, bulgar wheat, or couscous according to the directions, using salted water.

Combine the vegetables and cooked grains in a large ovenproof bowl or pot, and drizzle with the lemon (orange) juice.  Cover it and return to the warm oven (now turned off) for 10 minutes.