Preheat oven to 180℃/160℃ fan-forced. Place a third of the chickpeas on a large paper towel-lined plate. Top with another paper towel and pat dry. Set aside until ready to use.
Combine cumin, coriander, half of the garlic and 2 tbs oil in a small bowl. Place cauliflower on a large piece of foil on a large shallow roasting pan. Brush spice mixture all over cauliflower. Season. Scrunch up foil around cauliflower, then pour 1/4 cup boiling water into foil. Fold up sides of foil to enclose cauliflower, scrunching foil at the top to seal. Bake for 1 hour or until just beginning to soften.
Place pat-dried drained chickpeas on a large baking paper-lined tray. Spray with oil, then sprinkle with paprika and season. Remove cauliflower from oven and carefully open foil. Bake cauliflower and chickpeas for 40 minutes or until cauliflower is golden and tender and chickpeas are crispy.
Meanwhile, place 2 tbs of the remaining oil, half of the lemon juice, remaining chickpeas and garlic, and 2 tbs warm water in a food processor. Season. Process until smooth. Place tomato, onion, mint and remaining lemon juice in a small bowl and toss to combine.
Spread hummus on a large serving plate. Carefully transfer cauliflower to plate. Scatter crispy chickpeas and over half of the tomato mixture. Drizzled with remaining oil and serve with remaining tomato mixture.