Finely chop 2 of the garlic cloves, then place in a bowl with the chopped tomatoes and basil. Stir in 2 tablespoons of the oil, season well, then set aside.
Brush bread on both sides with the remaining 1 tablespoon of oil. Heat a chargrill pan over high heat, then grill bread for 1 minute each side until charred. Halve remaining garlic clove, then rub one side of the bread with the cut side of the garlic.
When ready to serve the bruschetta, pile the tomato mixture on top of the grilled bread. Top with rocket, drizzle with extra oil and balsamic vinegar, and garnish with parmesan.