There’s a new Sagittarius at Rosie O’Donnell’s house. The TV hostess, 37, announced that she has adopted a third child, Blake Christopher. The boy was born Dec. 5, one month premature, weighing 5 pounds, 5 ounces. “The baby is very healthy,” said Rosie. “He’s half-Italian, half hodge-podge.” Blake joins brother Parker, 4, and sister Chelsea, 2, both of whom were also adopted. “Everyone is delighted,” said the proud single mom.