Preheat oven to 400 degrees. Add cauliflower and garbanzo beans if using them, to a large roasting sheet and toss with olive oil, cumin and salt and pepper.
Roast for 20 minutes, or until florets are fork tender but still somewhat firm.
Meanwhile whisk the tahini with 3-4 tablespoon of water and salt and pepper to taste. Consistency should be like a thick salad dressing. Spread on the bottom of a serving platter.
When cauliflower is done roasting, immediately toss in the preserved lemons.
Transfer roasted cauliflower dish to the platter and set over the tahini. Top with fresh parsley and more salt and pepper to taste.
Notes
What If I Don't Have Preserved Lemons?
Preserved lemons are basically a pickled lemon. So if you don't have them in your pantry, capers make a great substitution. Capers will bring that salty, briny flavor to the dish that the preserved lemons do.