I did a google search for "growing knockout roses in containers" and it looks like it is very possible if you have a very deep container - at least 18 inches deep.
I have two half barrel containers I'd like to grow something in and I think roses might be a perfect choice. I think I'd plant one with pink roses and white roses in the other.
"Love all God's creatures, the animals, the plants. Love everything to perceive the divine mystery in all." -Fyodor Dostoyevsky