You are definitely going for the right look for a foundation planting, namely a layered series of different textures with evergreen at the back. But I agree that a total of 5 feet from foundation out is not enough width to get that job done. You have enough sun to work with and you have a vision, so why not do it up right: expand the bed 3-4 feet, move the roses out a few feet, and then put in some spreading yew or a globe arborvitae-type thing about 2-3 feet out from the house. You'll have to trim the yew or whatever you put there, but it will give you the look you want. Yews are incredibly overplanted on the foundation, but for the back row of a layered planting, I think they work just fine. Put a low layer in front of the roses, maybe some Blue Star Juniper, then you can keep the layered thing going on during the winter. The Blue Star is fairly slow growing, (especially living on the east side), so don't expect it to fill in quickly. Instead, cough up the cash and plant several. If you think widening the bed is daunting, just lay down wet cardboard on the turf and cover with lots of mulch. Then cut out wide holes for your plantings. The grass will be long gone in a year. Boxwood could work against the foundation too, but it grows like molasses. Just my thoughts, based on having been in a similar situation. Get what you want the first time around, so you don't have to do it again later.

Most of the clay soils in the PNW are quite nutrient rich - their problems lay more with difficulty in digging or poor drainage. I would second Al's opinion (very commonly held, btw) that individual planting holes should not be amended, nor should any fertilizer be applied at planting time. Amending individual planting holes in clay soil runs a very real risk of creating pockets of poor drainage - bathtubs if you will - as the drainage benefits of the loose, amended soil are lost once the water percolates through and hits the more impermeable clay. Amending entire planting areas rather than individual holes will alleviate this problem. Shrubs and trees established in the landscape typically need very little in additional fertilization. More fertilizer won't necessarily make them bigger and stronger but unneeded fertilizing can promote lush, leggy growth which is weak wooded and vulnerable to insect and disease problems. The performance of your plants are the best guide for applying additional fertilizers. If they display symptoms indicating a nutrient deficiency, soil tests will indicate what nutrients may be missing. FWIW, in my well established PNW garden, I fertilize very sparingly, generally only those plants with a reputation for being heavy nutrient users like roses and clematis or container plantings. I do mulch with a good quality compost at least once a year (twice if I can manage it on my schedule) and the compost supplies necessary organic matter to the soils as well as a low grade replenishment of primary nutrients. Many gardeners fall prey to the heavy advertising campaigns of the fertilizer manufacturers, swallowing their dogma that their garden will just not flourish unless they apply copious amounts of fertilizers (ie., Miracle Gro). This is simply not true - over fertilizing can produce more harm than not fertilizng at all. Keep in mind the old gardening axiom that if you feed and nourish the soil, you will feed and nourish the plants. Continue those applications of organic mulch. It will improve overall soil structure through the addition of organic matter, loosening the clay and improving drainage and create a beneficial environment for soil organisms to breakdown nutrients into a form plants can access.

Kind of guessing a bit on some of this but information is scarce. I believe out those 3 rose White Meidiland would be the healthiest and overall best of the three. That said I did have W M and it is a big rose not tall but wide. It also tip roots where ever the canes touched the soil. Mine would easily form a 12 foot diameter circle. I just did not have that kind of room. It would be great for a hillside. So that one is robust and easy to grow. I would stay away from Wedding Dress as the rose just came out and they seem to be getting rid of it already. I would also be leery of Blossom Blanket. Only because it has been around a long time and is recycled occasionally by places like Jackson and Perkins and Wayside Gardens. It sounds okay on Help Me Find but I just have a feeling that it would be a problem rose outside of dry environments. Perhaps someone else has grown this one. So a lot depends on what you need the rose to do. I have tried many ground cover roses. For a white ground cover the best I have found is a Kordes rose Innocencia. It's very healthy and a much smaller size which works for me. There is also a newer drift rose in white that looks good. Not really sure if it is a new and improved white or the old one that they used to sell. I do grow 2 Cape diamond roses. They are own root and have massive root systems. I do think that she would do well in poor soil as long as it's not too wet. She is a large shrub so give her room.

otherwise healthy .... and with no insult to the root mass ... this thing should return with a vengeance ... and you will probably be beating it back with a stick or a truck in a year or two ... if you do nothing .. a little of this or that rarely hurts anything .. properly applied .. but dont think it needs anything special.. i mean really .. its been there how long ??? ... and gotten how big ..??? not to mention... if you fert under a maple.. i can assure your that its aggressive root mass will come and steal everything you think you are giving to the other plant ... if its gotten leggy over the years.. its probably because.. as the tree grew.. its might not be in the full sun it would prefer ... imo.. waste of money .. but if you have some around for other purposes.. knock yourself out.. short of dumping half a bag around it ... ken