Frank,
In my experience, the roses from DA have performed well so far, both in the ground and in containers. However, they are all hardy against mildew and rust to a certain limit. For instance, in SF weather, growing roses is a challenge, and DA roses are no exception. I spray my roses every two weeks to keep them free of diseases.
The following DA link has roses suitable for zone 5:
https://www.davidaustinroses.c...
If you look to the left side of the webpage you have a list of filter options that you could use to sort roses that fits your preference such as rose type, color, height, fragrance, disease resistance, specific situation, challenging location, etc. In regards to own root and bare-root, it's merely a personal choice for I have roses of own root and bare-root that are growing and blooming well. Own root takes a while to get established, unlike bare-root. And DA only ships roses during the planting season suitable to your planting zone thereby ensuring the survival of the rose once planted. Clicking on a rose in the website will direct you to the product page where it will indicate if the particular rose is available in a 2-quart pot or as bare-root. Hope this helps.