Sure they will do well in containers, if you follow the very good advice available on this forum. Al

Out of curiosity, why Knock Outs? There are a wide range of roses that will work well in containers (check out Rose Forum). As a rose, Knock Outs are more of a landscape shrub as opposed to a container plant. They can get very large and unwieldy and are sheared to the ground in fall here by many gardeners in my zone to keep them in check. Since I'm such a different zone than you, I can't give any recommendations for alternate types, but there are quite a few California gardeners on the Rose Forum that could help you out.

They require the least care, and they have been marketed well and they bloom for a long time -
Not without problems, but many home owners do not have time a patience and knowledge for other roses.

Most repeat blooming roses grow for a long time. Knockouts are to roses what McDonalds is to food. Yuck!

In zone 9 there are so many tea roses that would be beautiful and easy care. There are a subset of Bermuda mystery roses as well. Just stay away from hybrid teas!