I would stay away from dish soap and use other soaps. Potassium salts are very good. It's fairly non-toxic. Here is the insecticidal soap I use. https://www.amazon.com/Safer-Brand-5118-Insect-Killing/dp/B00192AO90?crid=22J8TGNUPI667&keywords=insecticidal+soap&qid=1537560380&sprefix=insecticidal+soap&sr=8-2&ref=mp_s_a_1_2
the anti fungal is copper based. You can't use the stuff you find on Youtube bc most of those guys are in India where they have something that is illegal in the us.
heres the stuff i use
https://www.amazon.com/gp/product/B000RUASQE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
As someone who had three desert roses grown from seeds develop root rot (but are now thriving) - yes that's salvageable.
Get some good drainage soil - I use a combination of miracle grow potting soil, chicken grit (small, crushed limestone pebbles), and perlite - about a 1:1:1 mixture. Give it a decent sized pot, then water only when the soil goes fully dry.
You can try to kickstart some growth by watering with some 20-20-20 fertilizer. I use Jacks Classic 20-20-20 All Purpose Fertilizer https://smile.amazon.com/dp/B005LKNCZY.
Let it get plenty of sun and you should be just fine. For reference, here's the old root rot. It's now thriving.
I've been using BGI SuperGain, (which is infinitely better than SuperThrive) and Schultz All Purpose Liquid 10-15-10. Been using many Schultz products for as long as I can remember. Which brand are you using for 20-20-20? Have a bit of a time finding a good one.
Mine are all indoors unfortunately and pay for "sun" with the electric bill. Over 50 plant lights... 🙄
Forgot, I use a some pine fines as well. So go a little heavier on the sand. That's good to know. I use a good deal of sand for cacti & succulents.
Thank you!
Desert rose propagation is different from other succulents (where an offshoot can be snipped, dried and planted. I've only had luck with my desert roses when I cut off a more mature stalk, let it dry out for a day or two, then wetted and applied rooting hormone (this worked well).
I've used Jack's Classic 20-20-20 about once a week during growing season and it's worked out quite well for both adult (~12 year old), and from seed plants.