if you are defining groundcover as something to prevent weeds from growing, roses aren't. The proper definition is procumbant, meaning they grow low to the ground.
i know this is the rose forum, but daylilies would probably fit your bloom requirements and weed control more so than roses. of course you could probably plant some roses amongst the daylilies.

No, I'm not looking so much for weed control as for massed color during the summer, and no spray and self cleaning. Just trying to decide whether to order bare root Baby Blanket from J and P or to get the Flower carpets at the local Lowe's. We have Electric blanket at home, and I really like them, and they're truly no maintenance roses, so I'm leaning toward ordering them, but not looking forward to trying to dig the holes for bareroot planting on this hillside.

I haven't liked the flower carpet roses that I have purchased, although I have seen some beautiful pictures from this forum. I also have Electric Blanket and it is great! I purchased Roseberry Blanket last year and it is so easy to take care of, not a spot of blackspot, rust, or anything and I don't spray. I wasn't totally crazy about the flower, but Im glad that I tried it, once established the flowers were more double and this Spring they are a beautiful color.
Diana

I have 3 baby blanket roses on my slope that I like better than the flower carpet roses. They sprawl down the slope nicely! They bloom more and aren't as thorny. I'll post pics when I get time!

Immensee (Grouse) was the first ground cover rose "and set the standard for vigor and health that has never been equaled". Those words from the ARS Encylopedia. It is big, that is in length, rose growing as much as 13' in one season. Very fragrant but blooming only once, profusely.

Like most Kordes roses largely unknown here but available from Hortico, Heirloom and Rose Acres.

Does not smother weeds as mentioned above. Roots as it goes.

I have Roseberry blanket too, and I have it on a hill. I love it. It does very well. It gets some bs in my yard (everything does) but not badly. Since I spray everything anyway, I do spray it.

It spreads well and it's own root and will spread a bit. It gives great color. I also just bought Happy Chappy ground cover roses to give a bit more diverse color.

I hear you about digging on a hill. And think about pruning and fertilizing. You don't have to do either, but you will want to get up there once in awhile....

I had the original pink flower carpet on a flat clay damp spot for many years and it was a show stopper-- Huge and covered with blooms all season with little care. I planted three pinks and a white on a fairly steep damp clay bank five or six years ago and they have done very little.

Here's Baby Blanket on my slope.
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It is prettier than the pic, a bit darker pink.

Here's another baby blanket just beginning to bloom. I cut this one back severely and moved it in the early spring. I like the pink blossoms; it's been healthy and a good grower. BB seems to do pretty well in sort of shady places. I'm sorry, I don't know anything about flower carpet.

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Thank you so much for posting the pictures of the baby blanket rose. My husband and i have been looking for "real life" photos to compare to the catalog-perfect glimpses. After having seen these, I think that Baby Blanket is going to be perfect for our use as a low hedge next to the front walkway. We want something pretty, that will fill in the space without towering.

The Kordes ground covers are the best - Electric Blanket, Roseberry Blanket, Red Ribbons, etc. Kordes has their own agency in the US now. So you don't have to go to Canada for a source. Flower Carpet tends to sulk in summer heat. Although I've seen some plantings of Red Flower Carpet that look pretty good right now.

Don't go with flower carpet, unless you're willing to get up there and feed/water them on occasion. I planted them, in my sloping hillside front yard. They've been okay, but in order to provide the mass color you're wanting, they'll need some attention. Mine also got BS this year (everything did). They're okay.. just not the "plant it and forget it" that the tag implies. My neighbor's knock out roses look fantastic, but they're on a sprinkler system.
I have some Buck roses that have put out tons of roses all summer.