There are many things that you can use on fire ants that won't harm your roses. In fact I can't think of a fire ant product that will hurt roses. A good start might be to use Amdro in the general area and the foraging workers will pick it up and carry it back to the mound.
Regarding the Joseph's Coat, I'm not sure what you are worried about the other roses catching. I would plant it as most all rose diseases are so ubiquitous that one rose is not going to really affect another. The rose needs to get in asap anyway as summer is coming and planting later is more of a risk.
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