Combine first 9 ingredients. Divide mixture into 6 equal portions, shaping each into a 1/2-inch-thick patty.
Place patties on a grill rack coated with cooking spray; grill 5 minutes on each side or until a thermometer registers 160°. Remove from grill; let stand 5 minutes.
Place rolls, cut sides down, on grill rack; grill 1 minute or until toasted. Place 1 patty on bottom half of each roll; top each serving with 1 tablespoon sour cream and top half of roll.