Sorry, I can't be Julie and reply to your posts, gotta be Unique. Your posts
don't show up on Google any longer.
FWIW, since I live in flat Florida, I would add the edging for soil support.
Besides keeping the soil in place, I like the effect it would add to the bed.
I can't comment on any of your rose choices, not familiar with any of them.
But I do love the color combinations!

"Shiva" writes:

I plan to pound in some of that black, foot-high, rubbery edging at the
bottom, inside the existing 18 inch concrete retaining wall. Should I do
this below each row, in a kind of mini-terracing effect? Soil does wash
down, I had to add a few bags to Mutabililis throughout the year.

Thanks for all and any input. (Even if you hate these colors together, and
I know lots of you probably do!)