Set the beets, garlic and rosemary on a large piece of aluminum foil. Drizzle with 1 tablespoon of the olive oil, sprinkle with some salt and pepper and add a splash of water. Fold the foil up into a pouch and seal the edges. Transfer to the oven and cook until the beets are easily pierced with a knife, 45 to 50 minutes. When done, remove the beets from the pouch and set them aside until cool enough to handle. With a paper towel rub the skins from the beets. Cut the peeled beets into bite-size cubes. Mince the roasted garlic.
Combine the beets, garlic, chickpeas, red onion, pickles and lemon juice in a bowl. Season with salt and pepper, drizzle with the remaining 2 tablespoons olive oil and toss to mix. Transfer the salad to a serving platter. Sprinkle with the cotija and cilantro and serve.