Light a grill or heat a grill pan. In a shallow baking dish, combine the remaining 2 tablespoons of olive oil with the rosemary. Season the bass with salt and pepper and coat the fillets with the rosemary oil. Grill the bass over moderately high heat, skin side down, until nicely charred and crisp on the bottom, 3 minutes. Turn the bass and cook until just opaque in the center, 3 minutes longer.