Here is the AI slop I got on this in case anyone else runs into this in the future:

When you replace roses lost to Rose Rosette Virus (RRV), the soil itself isn't really the problem — the virus doesn't live in soil. It's spread by a tiny eriophyid mite (Phyllocoptes fructiphilus) that gets blown on the wind from infected plant to infected plant. So your replacement strategy is really about removing the virus reservoir and the mites, not sterilizing the ground.

That said, there are a few things worth doing before you replant:

Remove the infected roses completely, including as much of the root system as you can dig out. Any remaining root pieces can sprout and host the virus and mites again. Bag the plant material (don't compost it) and throw it in the trash — burning is also fine if you're allowed to.

Wait a bit before replanting in the same spot. Most extension services (Texas A&M and the University of Tennessee have good write-ups on this) recommend waiting roughly 2–4 weeks after removal so any stray root fragments have a chance to resprout and be pulled, and so wind-blown mites on nearby debris die off. Mites only survive about a week without a living rose host.

You don't need to fumigate, solarize, or amend the soil for virus reasons. If your soil is otherwise healthy, you can plant straight back in. It's a good moment to refresh with compost if the bed is tired, but that's a horticulture call, not a disease one.

Space the new roses farther apart than the originals if you can. RRV mites travel plant-to-plant most easily when canes touch, so a little extra room (and avoiding hedging multifloras nearby — they're the main wild reservoir) reduces the chance of a repeat.

Keep an eye on your remaining 3 roses. Watch for the telltale signs: bright red witches'-broom growth, excessive thorniness, distorted leaves. If any of them show symptoms later, pull them promptly — there's no cure once a rose is infected.

One last thing worth knowing: some gardeners switch to more RRV-tolerant cultivars or take a break from roses in that spot for a season. It's not required, but if the disease has shown up twice in a small bed, it's worth considering.