Rooted clone ready for transplanting...
The roots could be a little shorter for good soil transplanting, but no longer than these roots…
Let the roots get no longer than in the above pictures, in fact shorter than that is better. Preferably about 1/2" long. Carefully place them in the soil and water them in very wet…soaking wet, then let the soil become almost bone dry, by then the clone will be hardened off and rooted into the soil nicely.
If you allow the clone to develop the long water roots it will not adjust very fast and stall for about a week or more, so transplant them at or before they are 1/2" to 3/4" long. The drying down from soaking wet soil drench will encourage great rooting into the soil. Use a weak high P fertilizer, preferably with b1 or with superthrive to really get the root system established into the soil. After you’re seeing new growth you can switch them over to weak High N ferts…but be carefull about increasing the nute strength at first, you dont want to fry the newly developing root systems.
Too long for soil…
The roots in this picture (from Sportsters bubbler cloner) are way too long for a good transplant to soil without stalling. However, they’d be just fine for a hydroponic system transplant, DWC for example.