Sylvie,roses are really not difficult to grow,probably easier than many other plants.
You just have to start with a nice healthy plant from the nursery.
I've never bought those roses packed in plastic,I believe it's always better to buy a potted rose,a little more expensive,but worth it.
All they really need is water and sunshine and if aphids appear,have them removed.
I have about 15 rose-bushes my pink one is more than 30 yrs old.
"The cruelest animal is the Human animal"
3 kitties,Rocky(r.i.p my boy),Chico,Vinnie