Garden center

I drove up to our local garden center Sunday morning, since I hadn't been up there for over a month.  I wanted to buy some cosmos and zinnia seeds.  They didn't have any that I wanted.  Instead, they had some strange looking cosmos and NO zinnia seeds.  But, camera in hand, I wandered around and enjoyed seeing all their plants!  :-)

Why can't I grow roses like these?  I've given up on roses.