I generally try to bury the rose so that the bud union is a little below the surface of the soil. I'm not very good at mulching, though I know I should. I'm also not good at improving the soil. I'm sure that if I piled on enough good mulch, I could get earthworms to help out a lot.
What I do know is that some roses seem to soldier on regardless of the many insults they are dealt, and some just die if you look at them cross-eyed. I'm also learning that planting early in the year works best for just about all the roses. Fall planting has a fifty percent mortality rate here, even for own-root roses. It seems to be true even for roses planted in September - though perhaps not mid-August. Finally, I'm learning that some roses that are fine with zone 6 weather perish in winters here, in what is now zone 8. Gardenia, for example. I'm sure that if I had a big enough pile of mulch on it, it would survive.
