When I find a rose with crown gall and I'm afraid some of it may have broken off, I disinfect the soil with a 5% bleach solution. I take a 5 gallon bucket filled with water and dluted bleach and drench the area of the bush. I replant as soon as the water has drained.
If none has broken off, I don't bother to disinfect. The bacteria that causes crown gall is in the soil naturally and I'm not about to disinfect my whole yard.

I've always heard you aren't supposed to plant a new rose in an old rose 'grave', but I broke that rule just yesterday! Although the rose has been dead for over a year or so and died because of deer browsing.

Also try to avoid damaging or dinging the new rose. The bacteria gets into the plant through wounds.

From Google:

Unlike black spot and powdery mildew, crown gall (Agrobacterium tumefaciens) is a soilborne bacterial disease which infects root and/or stem tissue rather than leaves. Galls are most frequently seen as round, rough-surfaced growths near the plant's crown or on roots. These "crown" galls will eventually girdle the plant, resulting in poor growth and eventual plant death.

Crown gall is a difficult disease to control once a plant is infected. It is best to remove diseased plants as soon as they are detected. Where possible, remove and discard all soil in which the root system is growing and replace with sterilized soil. If crown gall is a recurring problem in an area of your yard, it is best to rotate the area with a nonsusceptible grass crop for 3 or 4 years.

Where a gall is restricted to stem tissue only, cut off the entire cane and immediately seal the cut surface with glue. Always sterilize cutting tools with rubbing alcohol after each cut of a cane with crown gall.

During and after planting, take special care to avoid any and all wounds, especially near the soil line. Provide good winter protection to prevent bark cracking or other cold injury to bud union area. Never use crown gall-infested soil to mound over bud union for winter protection.

Thanks for the info/advice Karl, mersiepoo, hoovb & decobug. I'll take 'ol George Burns out and think about what I want to do with the empty spot. I wonder if I could just do the water/5% bleach soil wash, and then use that area to plant some flower seeds instead. I have LOTS of seeds and not enough places left to plant! :0) Phyl

I followed Karl's advice a while ago for this same situation and have had great results. New rose is growing well and no sign of any galls on it or surrounding roses.

I found this Canadian document approving Dygall, a biological control. One dips roses into it before planting into infected soil. A New Zealand study showed a reduction in infection of 23% to 1%--and the ones that were treated ones that became infected showed much smaller galls.

A. radiobacter strain K-84

Here is a link that might be useful: AGROBACTERIUM RADIOBACTER

I did some web searching and found a competiting product, called Nogall.

Here is a link that might be useful: Maker of Nogall

My understanding and experience are limited. However, I have successfully replanted in the same hole with the same soil where a rose infected with crown gall came. Crown gall often enters a rose through damages to a cane at soil level. That is how I lost mine, through careless hoeing. I am simply more careful now, but resist the urge to treat the soil with anything. I have also seen on particular rugosas gall caused by wasps. The canes were removed.
Steve.