My parents, my wife and son, and I stayed in Roca Blanca for 3 days in December, and had a fantastic time.
The apartments have quite possibly the best view in Viña del Mar. They overlook the castle and ocean, and are centrally located to walk through Viña.
We had a 3 bedroom apartment, and it's spacious enough, with a full kitchen, refrigerator, and 3 showers. The showers were a bit small, particularly the guest shower. That aside, it was fine, and we continually marveled at the view from the beautiful balcony.
There is a swimming pool as well, and they have an elevator that puts you right out onto the malecón to walk into town, where there are a ton of great restaurants.
It's really an ideal spot for Viña, overlooking the coast, and a great place to relax. Prices were very reasonable as well. Definitely recommended for both couples and families.