Place cauliflower florets in a food processor and pulse to form rice-sized pieces. 

In a medium bowl, mix the lamb, allspice, cauliflower rice, salt and pepper in a bowl until combined well.

Carefully open each grape leaf, placing the rib-side down onto work surface. Place 1 rounded tablespoon of the meat mixture into the center of the grape leaf. Fold the bottom of the leaf over the meat, fold in the sides, and roll tight into a cylinder.

Stack the grape leaf rolls in a single layer in large pot, covering each layer with slices of garlic. Add just enough water to cover the rolls, then pour in the lemon juice. Place a plate on top of the rolls to keep them submerged.

Bring to a boil, then reduce heat and simmer until the cauliflower rice is tender and the meat cooked—about 50-55 minutes. 

Drain water and serve.