While I used some of the beet greens in my Thanksgiving centerpiece, I roasted two bunches of beets for my ensalada de remolacha. One thing I love about Encarnacion Pinedo's cookbook: very few measurements and bare bones descriptions of how to make the dishes.
I sliced off the greens and tips, washed the beets, dried them, sprinkled them with smoked sea salt, drizzled them in olive oil, and roasted them - covered with foil - in a 350 degree oven till you can pierce them with a fork. The cooking time depends on how big the beets are. These took about 75 minutes.
Once the beets cooled, I peeled them, sliced them into eighths and seasoned them, according to Encarnacion's instructions: sprinkle with salt, pepper, and cumin. Drizzle with olive oil some vinegar. She suggested sliced raw onions; I skipped those.