From what I understand, the bacteria that causes crown gall is in the soil everywhere and really can't be avoided. It enters a rose through an cane whose camber has been compromised, say by a hoe when weeding. I would simply go ahead and plant another rose, but there may be others who reply to your query with more plant science behind their answers than mine.
Steve.

This link is to an award winning article on the subject:

http://www.marinrose.org/crowngall.html

Here is a link that might be useful: link for above

There is research that biological control appears to be helpfull:

http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-98-11-1218

Also some roses are more resistant than others:

http://www.actahort.org/books/767/767_53.htm

Thanks, Henry.
At the http://www.actahort.org/books/767/767_53.htm site, the authors speak of the 'wound' where the bacteria enters. The consulting rosrian, Nanette Londeree, suggests that one should not replant where crown gall has taken out a plant, but I have successfully done so. Perhaps it is dumb luck, but I would replant one in the same place if it happened again.
Steve.

elks, perhaps your first rose brought grown gall with it and your replacement rose did not have any "wounds", and/or was naturally more resistant, and or/some other local condition (acid/basic soil/temperature/moisture content, etc.) which was not favorable to natural spread. Most biological "conditions" are very complex.

Here where crown gall is a problem, UC davis recommends...

--good sanitary practices & wound avoidance
--solarization of the infected soil
--an innoculant called "Agrobacterium tumefaciens K-84"

I replanted where I removed a crowngalled rose. I removed a lot of soil, replaced with fresh from another area, and made sure there were no wounds on the new rose. 4 years later, no sign of any gall (yet). I piled the old soil and solarized it.

Here is a link that might be useful: crowngall suggestions from UC Davis

Aspirin to the rescue?

See:

http://www.plantphysiol.org/cgi/content/abstract/146/2/703

Here is a link that might be useful: link for above

Melissa,
I've successfully stopped crown gall on my roses that have become infected with it by carefully digging up the bush then removing the gall(s) and a thin sliver of wood at the point where it was attached. Because it's a bacteria, I spread some cheap generic antibacterial ointment on the wound. I then mix two cups of bleach in a five gallon (19 liters) bucket of water, and pour this over the soil in the hole from which I removed the bush. After the bleach water drains from the hole, I replant the bush from which the gall was removed.
I've never lost a crown gall infected bush when I followed this procedure. After replanting. treat as you would any transplanted rose bush.

Thanks, everybody, for your help in dealing with this problem. I appreciate your information and your taking the time to answer!
Melissa

Also be alert for aerial galls on canes and branches. If you prune a gall and continue pruning without sterilizing the tool, you can get many galls developing in the pruning wounds.

A good point, and one I am now keeping in mind. All this input made for interesting reading. Thanks,
Melissa

Some years ago we used Galltrol - which is "produced from a culture of the naturally occurring strain of Agrobacterium radiobacter (strain K-84) grown on a scientifically defined agar medium"* to combat crown gall that seemed to be confined to a small area of the yard (I know the bacteria are said to be present everywhere, but that was the area we noticed infected roses). Used it to drench roots before planting young roses and we never had the problem again. Don't know if Galltrol is available everywhere, but perhaps it's worth a try? Pat
* Directly from the AgBioChem/Galltrol website.

I never know where to find these things in Italy, which is one reason my gardening is so primitive. I'll keep it in mind. Thanks for mentioning it.
Melissa