I just added Eutin/Hoosier Glory this spring after seeing some photos of it. Seems to be what you are looking for too...

Tammy

Here is a link that might be useful: Eutin

Look at 'Home Run' and how it does in your area. It might meet your requirements.

I have and love Cadenza and Cameron Bohls - I let mine get fairly large but they could be kept pruned to a smaller shrub. They are disease free and bloom constantly.

3 feet is short for a shrub, even Red Flower Carpet may get a good bit taller than that. Red Drift provides constant color & is healthy here and it's short.
Others-- Champlain and Dublin Bay-- would be MUCH taller, not sure they could be kept to 3 ft.

Try to find out how Lavaglut does in your area. I am in a very warm climate and it blooms alot and the blooms last long in the heat. It is a dark red with small blooms.
Here is a photo of the bush. It is much too bright red--imagine a very dark red:
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The new one called Thrive! is definitely the way to go for that request. See, Rose Hybridizer's Blog and then scroll 3/4 of the way down to July 30 2011 post.
It's new this year, but I've been growing it for a year -- it's a good one. Another one worth looking at though, if you also like yellow on the reverse of the blooms is Ketchup and Mustard.

Both Thrive and Ketchup are extremely healthy. Ketchup and Mustard has better form on bigger blooms -- higher centers and longer lasting, but Thrive has many more of them, so it depends on what you want. Both of them are healthier than anything that has been mentioned up to now, above.

Kathy