On a work surface, mash the garlic with a generous pinch of salt until pasty. Scrape the garlic into a bowl and whisk in the buttermilk, yogurt and cider vinegar.
Whisk in the canola oil and season the ranch dressing generously with pepper.
In a large, deep pot, bring 1 inch of water to a boil. Set the broccoli in a steamer basket and steam until bright green and crisp-tender, 4 to 5 minutes.
Transfer the broccoli to a plate and refrigerate until cool.
Meanwhile, in a skillet, cook the bacon over moderate heat until it's golden and crisp, about 6 minutes.
Drain on paper towels.
Arrange the bacon strips on plates and top with the broccoli wedges.
Drizzle with the ranch dressing, top with the Roquefort and sprinkle with chives.