The lobby of Rosewood Post-Acute Rehab, a nursing home in this Sacramento suburb, bears all the touches of a luxury hotel, including high ceilings, leather club chairs and paintings of bucolic landscapes. What really sets Rosewood apart, however, is its five-star rating from Medicare, which has been assigning hotel-style ratings to nearly every nursing home in the country for the last five years. Rosewood's five-star status — the best possible — places it in rarefied company: Only one-fifth of more than 15,000 nursing homes nationwide hold such a distinction.