WOW. That's an impressive project. I am trying to take it all in. First of all I am impressed you have a HILL. In Florida! Yes I know central florida has hills because I just crossed the middle of the state and saw some but didn't know that Tampa had any. You are lucky to be on a hill. Second of all I am impressed with your list of roses. Just awesome. So...is the area at the top enclosed by the wall going to be level with the ground when it's filled in? It looks that way. And then the area outside the wall is stepped down 4-5 feet? The very first thing that comes to mind is safety to keep people and animals from wandering off the edge and falling over (I'm clumsy myself) so I would think about a solid hedge and/or fence around the back and high parts. You could put climbing/rambler roses trained horizontal along it, maybe a split rail fence there. A solid hedge might work too but then you couldn't see your rose garden from the street side. Perhaps rather than planting something at the top that trails down you could do an espalier on the wall below. There are so many vines to choose from. Or you could espalier the Don Juan rose you have.I'm not familiar with the other roses to know if you have other climbers but mixing two different colors with different bloom times would be cool. I know what you mean about needing something to interplant with the roses and I don't have anything specific to reccomend but can suggest putting some of your roses in decorative (large) pots. That way when they don't look good they can be rotated out to a less visible area. My favorite sun loving plant is perennial verbena. It's pretty low maintenance, comes in lots of colors (except yellow or orange). I also love daylilies for the same reason. Sorry for the long ramble-on. I look forward to hearing other peoples ideas. It's fun to imagine your finished project.

I am on the 8b/9a border, and a few of those suggested plants are very iffy for winter survival here: bougainvillea, ponytail palm, jatropha, and plumeria are all likely to die without significant winter protection. However, you can overwinter a potted plumeria in a dormant state in a cool, dark (but not above-freezing) location such as a garage. Potted ponytail palms can be easily overwintered in the house, since they are happy in the dry heat. There are also many plants on that list that will reliably survive the winter, but will defoliate or even die back to the ground in the cold. Some of them are plants that are evergreen in central/south Florida (hibiscus, passion vine, etc.). You asked for perennials, so maybe you don't mind winter die-back, but I thought I'd mention it. If you want something evergreen to add some height and structure, you can use Indian hawthorn (as Carol mentioned above) or ligustrum. For a deciduous shrub or small tree, crepe myrtles (mentioned above) are great. If you get a bigger type and let it keep most of its crown growth (no coppice pruning, a.k.a. "crepe murder") it will eventually make a nice tree and give you a partly-shaded area to plant under. Knockout roses (mentioned above) grown in full sun will reach 5'-6' or more in a couple of years if you don't cut them back too aggressively. If you keep them cut back, you can maintain them at 3'-4'. They will defoliate briefly in the coldest part of winter, but generally don't drop their leaves until the hard freezes hit - so often they are green past Christmas. For edible landscaping, the blueberry bush (decidious) can be attractive. It has white flowers in spring, of course followed by the tasty berries. The dwarf Sunshine Blue only gets 2'-4' tall and has pink flowers. Blueberries love sun, but you have to maintain an acid soil. For an unusual color on a bigger shrub - IF you are willing to mulch very well and water regularly - loropetalum will do great in full sun. It has beautiful purple foliage and the brilliant pink flowers in spring are a bonus. My next door neighbor has some beautiful ones, and there are several apartment complexes and shopping centers that also have lovely ones that get all day sun. I am not kidding about the mulch and water, though - they will die or look terrible if you stick them in full sun without adequate mulch and moisture, and I'd wait until fall to plant them. They will need the cool months to get their root systems established before facing the heat next summer. Their foliage is much denser if grown in full sun, dense enough that they can be pruned into shapes - rounded top shapes are popular around here. The native saw palmetto or the king sago (cycas revoluta, which I believe Carol mentioned above) can be an effective backdrop or centerpiece for your perennial flowers, too. They are almost bulletproof. Ornamental sweet potatoes are a pretty ground cover to weave among your flowers. While they are not supposed to be hardy, mine have come back after the last two winters. Mine are out in the brick mailbox planter exposed to dawn to dusk sun along the street. However, the grocery store sweet potatoes I planted with them (some that had sprouted after I failed to cook them soon enough) have grown even more vigorously. I leave them in the ground all winter. One last thought: I bought some pretty purple African Daisies from HD this spring. They have done really well, repeatedly blooming in sun and poor soil with no deadheading. They were labeled as perennials, but since I just got them this year I can't report on their actual hardiness yet. Good luck!

Well,I'm not in the frozen tundra,but I'll tell you what I know about this hosta. It is a sport of Fried Bananas,an all-gold sport of Guacamole. All of these hosta are very sun-tolerant. Here is mine,planted just this year,and it is in a place where it will get morning sun until noon. My Fried Bananas is planted in the same conditions. You shouldn't have any trouble with yours in lots of sun. Phil

Michelle, I agree that 2011 was truly horrible. We were out fighting wildfires day and night and were living on Gatorade, bottled water and whatever food I could grab in a hurry and take to fires. Forget watering the garden....I was watering firefighters. It was the worst summer ever with more firefighters sick from the heat than you can even imagine, including me. It ruined me for gardening because once you've had heat exhaustion or heat stroke, your body cannot tolerate heat the way it once did. After a lifetime of being very careful to take care of myself out in the heat, I blew it that summer----not from carelessness, but just because the demands for assistance at fires were so high and I couldn't ignore them. Nowadays I no longer can stay out and work in the garden for as long as I want....I have to come indoors before it gets too hot, which cramps my style and makes me cranky, but I do it anyhow. I don't want to ever get too overheated again. This should have been an easier summer than it has been. We've gone 61 days now without receiving 0.25" of rainfall on any one day. At our house, our total rainfall in that 61 days is 0.13", meaning our dry spell here this summer has been more prolonged than our worst dry spell in 2011. What has saved the trees, at least, is that we had roughly 54" of rainfall this year (our annual average is 39") before it stopped raining. Our upper level soil moisture is 0.0 in the upper few inches of soil, but there is good soil moisture a couple of feet down. Our Keetch-Byram Drought Index at the present time is almost as high as it was during the worst of 2011. In 2011, I understood what was going on as the drought developed throughout the year....even back in the winter and spring as we headed into summer, so watching it was like seeing a train wreck coming.....This summer's Flash Drought has been harder to fathom because it came out of left field so abruptly, beginning while we still had roads and fields under water from the flooding. On the last day that it rained, we had no idea it was "never" going to rain again for the next couple of months. If we had, we probably would have enjoyed the flooding more than we did. It is 102 degrees here today and just so danged hot, and there have been fires in the area, but not in our fire district. (Knock on wood!) The cold front is supposed to come through here overnight and to bring us blessedly cooler temperatures and rainfall. I can't wait, and I'm gonna be one mad gardener if the rain misses us again, although I'll still enjoy having highs in the 80s or lower 90s instead of in the 100s. Our next door neighbor in Ft. Worth had the old hardy neon pink-flowered phlox commonly referred to as thrift. I loved hers, but I didn't have luck with it in our blackland prairie clay (right next door to us she had a much sandier soil), and I've never planted it here. We do have the native phlox that blooms in spring here. It lives happily in the bar ditch down by the road, where presumably it gets enough moisture from rain runoff to keep it happy....and Tim isn't allowed to mow it until it has finished blooming. On upland areas, we stay too dry for the native phlox to thrive, so I have to make sure we leave it alone and don't mow it back too early in the one area of our property that has enough moisture for it. It was gorgeous this year in April, but drowned in May's 25.5" of rain. Dawn