Moondog, as you get more experienced with roses you'll be able to do for yourself what the helpful employee did for you, and that's to pick out the "best" plant among many others. It's tempting to look at the top growth and be drawn to whatever looks bushy, full of foliage and in bloom. But I do the opposite:
The first thing I do is pick up each plant and hold the pot at eye level, or if it's too big, I tip the pot at a horizontal 45 degree angle, so that I can look just above the rim of the pot at soil level, and count how many canes are sprouting directly out from the bud union (the woody bulb just above the roots). And I make sure to observe how many of those canes are healthy (not split, broken, torn or dying back), and how many of them have healthy branching off-shoots. (The thickness of the canes also matters.) To me, the more canes, the better, even if the top growth doesn't look quite as lush as some other plants. Roses are very fast growers, and the top growth can change quickly, so for me I'm more interested in the structure of the plant. (Of course, for me in the northeast, I'll be pruning a lot of those canes off each year after they die back from the winter, so who knows how many canes it will produce in subsequent years. But I at least want the maximum number of healthy canes to start with.)
The second thing I do is look at the top growth. If the roses are showing signs of black spot, powdery mildew, or insect damage, I'll look for one with healthier foliage. This is where it can get a little tricky, because sometimes the plant with the best structure might have more blackspot, so you have to use your judgment and make trade-offs.
Whether or not the plant is in bloom at that moment is less important to me than its structure and health, as per the above considerations. The only time I'm really drawn toward a blooming rose when making a buying decision is if it's a toss-up between it and a few others of equal quality. If one of them is in bloom, that's the one I'll take home.
The one I have is grafted and I'm considering trying an own root one to see if there's any difference in growth improvement. Here you can see the full range of aging purples from new blooms to old. 
