Rosemary ...
It is always easier to start out with a healthy plant. At least now you know what to look for when you are purchasing a rose from a big box store ... or any nursery. Mail order ?? You get what they send ...
I have had canker on roses that I have purchased from nurseries up here, but I didn't plant them out right away. I have lousy, lousy native soil in this garden, so I have learned to pot up my roses in good soil and grow out a large root mass
before I put them in the ground.
None of the big box stores, or even the two good nurseries, sell bare rooted plants up in Redding. The roses are all potted up. I've been told that is because the mortality rate is too high to leave them as bare root plants.
I don't know if you are aware that roses are harvested by machines. They are yanked out the ground and thrown on a truck to be hauled to the processing area. The roses that go to the big box stores are the culls ... they have more machine damage ... damaged roots or very few roots ... than the roses that are sent to the better nurseries. So, they are starting off damaged.
You may already know what practices you should follow when you bring a new rose home, but others on the forum may not. I am only referring to roses budded to Dr. Huey, not multiflora, because I have only grown roses budded to the good doc.
There are a few things you can do when you first get your rose to make sure it has a better chance of succeeding.
When you bring your rose home, you should inspect the roots for any damaged or rotten roots and trim them off. Then you should soak the roots in a 10% bleach solution over night. This should kill any fungus growing in the root system. (Note: I would do this even if the rose came home potted up because I am certain this step is skipped at the big box stores.)
Then pot the rose up in a clean pot with good potting soil that drains well. Keep in mind that there is no way that you can do this without damaging the feeder roots of the rose. What that means to you is that the root system is inefficient and not working at 100%.
Good practice is to water the rose every day while it is growing new roots. Roses will not put any energy into the top growth until they have a good root system. Don't feed the rose until you see new top growth. That is the signal that the root system is now working and the rose is ready to grow. Then feed it lightly and often.
I don't even put any fertilizers in my pots, while others will put some organic fertilizers in the pot.
A few years ago,
@Zuzu recommended that the soil in roses purchased from a nursery that have been potted up should be replaced because the nurseries use a potting medium that is more sawdust than soil. I think that's a good tip.
I know this sounds like a lot of work, but I've never ended up with dead roses, so I think it is worth it.