Greetings all. So I have been

Greetings all. So I have been taking clones, dipping in root hormone and sticking in soil with a bag over the whole thing. They do quite well in this set up but I'm wondering how I'll know when they've grown roots? Will they eventually start to put on new leaves thus letting me know that the roots have taken hold and I can now remove the bag?

new leaves is the clue that roots formed.