Bring a large pot of water to a boil. Add Romanesco cauliflower florets and cook until crisp-tender, about 3 minutes. Drain.

Melt butter in a large skillet over medium heat. Add garlic and cauliflower florets; cook and stir until tender, about 5 minutes. Sprinkle parsley over the florets; cook and stir until flavors combine, 2 or 3 minutes more.