How about Perle d'Or. Easiest rose I grow. Bush is always blooming.

Also consider Easy Elegance roses such as Kashmir. Check local nursery
http://www.easyelegancerose.com/

Here is a link that might be useful: Kashmir

Very few (none) roses will be evergreen, much less everblooming in zone 6. That said, a great many Hybrid Musks and Polyanthas are 'continuous' bloomers, continuous meaning from May thru Oct. They come in all sizes and colors, including some, such as Weeping China Doll and Red Cascade, that will drape over the wall.

thank you for the suggestions. I should have been more clear - I meant ever blooming throughout the growing season. Our winter nights can get in the single digits on rare occasions!

One important thing I do need is for this bush to be upright. The wall already has a hardy variety of Caroina Jasmine growing along the top and cascading over. This shrub is needed to soften and improve the looks of the unsightly hill that is being held back by the retaining wall.

Will definitely look into those that are suggested.

thank you!

Belinda's Dream (pink) is wonderful down here, not sure about your area. I don't grow it, but Julia Child (yellow) is gorgeous in the gardens I have seen it in.

Belinda's Dream gets 6-7' tall and wide, and you can really see the "legs" on her. Julia Child would be a good choice if it can take the climate, I think.

Knockout has a lot of press, and too many landscapers are using it, so thanks for wanting something else. To me, it's the new ligustrum.

If you don't mind something that will get taller and bushy, there are a lot of OGR shrub roses that might work. Such as Blush Noisette, Mme Joseph Schwartz, Mrs. B.R. Cant, to name three.

Mrs. B.R.C gets much larger than BD in my garden. BD is bushy all the way to the ground and extremely healthy. No bare ankles here. She's on Fortuniana here. As they say, YMMV. Natchithoches Noisette, own root, is a beautifully rounded, healthy four foot rose here. Is Zone 6 too cold for Noisettes?

You might also try Rugosas. They are nearly maintenance free. They will take the cold, many are nearly continuous bloomers if it doesn't get too hot, don't need to be sprayed, and most have good autumn color and lovely hips. Many also sucker, so if you are looking for a 'hedge' they will grow into it easily.

Hybrid Musks and Polyanthas have more the knock-out look, but you want to be careful on size, as many of the HMs can get quite large and the Polys can be very small. Both will handle zone 6.

Hybrid Teas and Floribundas require more work and are less cold hardy even on grafts.