You don't need to worry about grafted roses there. Be careful if you plant early, though. You might have to protect your new roses if you get a late frost. (a cardboard box will work fine, a rock on top will keep it from blowing away). That's the reason your local nurseries don't start selling them earlier. If your new roses start sending out tender new leaves and they get zapped by frost, it could kill the plant.
I like buying roses for my daughter who lives in Utah from Regan Nurseries - they're in California.
http://www.regannursery.com/
But there are many more rose growers over on the Roses forum that will also have their favorites - more choices for you.