Most of the roses you're going to see at Costco and home center type places will be grafted tea roses. You may get a good one; that said, they are all going to be grafted, not own-root, which means that if you live in a colder climate, they are unlikely to make it through the winter. I have bought roses at home centers and had them do very well; they were potted and not bare-root, and they were all marketed as "shrub roses."

My experience with Costco's bareroot roses and blueberries and bulbs has been uniformly negative -- I have yet to have any of them live through a year. The prices are so low because the stock is just not cared for as it would be at a nursery. I get most of my groceries at Costco, but I won't buy plants there any longer.