I'm wondering the same thing, my cuttings always seem to go black at their bases indicating that they're over watered and are rotting. But where is the fine line? I have literally no idea...
I cannot for the life of me get rose cuttings to root, they seem to grow a few small leaves looking like they're doing something, but then the cutting stem just turns black at it's base! I could be over-watering them, but how on earth are you supposed to know exactly how much water they need before they rot? Then when I check to see if they've rooted by pulling them out after a month, there's fucking none! I don't get it!!! 🤬
Mine was inside because it was still cold outside, but as the temperature went up i put them outside. It needs atleast 10 to 15 days for the leaves to come out, depends on the temperature and how much light it has.
You wait for the leaves to come out and when you see that the leaves are close to the sides of the cup you slowly adjust the rose to the outside without the cup and you let it grow until it has roots and transplant in the garden
Spring is the best time, so it has time to grow and prepare for the winter but if you dont have really cold and freezing temperatures you can plant them whenever.