i wouldn't dig it all out and replace. I would just grind everything up and dump on top. the worms will take it from there.

Compost.

Check out chilipete's thread Best way to improve soil.

Also, the Rutgers Extension Service has several publications on composting (I'm a half-hearted composter, but I try).

Monmouth County (Middlesex too, I think) holds courses from time to time on composting.

Here is a link that might be useful: Rutgers Extension Service Composting bulletins

Clay is good-- the very best soils have 15-40% clay content. Even a sticky clay soil can be fine for roses if you handle it right. That means not messing with it when it is moist enough to model. Don't dig, till, or step on it unless it is dry enough that clods break rather than mash when you bap them with a shovel.

What len511 suggests is true. If you keep a thick mulch on top, the organic matter will modify the soil several inches down within a few years, and the top 4" is the most important to roses. Also undisturbed clay will develop a structure of plates and cracks that will allow some deep drainage.

It might help plants get started if you can till 3" of organic matter (compost, peat, bagged manure) into the upper 6-8" of clay when the soil is dry enough to work. Do the whole bed rather than planting holes. Texas A&M is recommending an additional 3" of a new product, expanded shale, mixed into clay topsoil to lighten it and raise the bed level for better drainage. I've no experience with this.

Starting a new bed, I'd get a soil test to check especially the phosphorus and pH so you can adjust these, if needed, when you till. You may find that the clay already has high levels of most nutrients.

Thanks so much for the information. I do compost, of course, and most of my flower beds are in good shape. But removing bushes that have been there about 50 years presented me with this challenge. I'll build up the bed a bit, and just load it with compost and mulch. It is now too wet to "bap" the marl with the shovel. Cute word,michaelg! I understood exactly what you meant.