So great to hear that you're working on the Banjo Rolls lesson! It's a big lesson with lots of information and the level of the examples are advanced. When it comes to the bpm, and when you can move to the next example;
For me, I've always thought of it like this: If I want to learn how to play something really fast, then I need to practice it slow for a long time first until it's in my fingers and I don't have to think about it anymore. Then increase the tempo. BUT, in a lesson like this the most important thing is to keep things interesting to yourself - in other words - staying for too long on one example can be quite boring, and to be able to learn something new, we have to stay inspired. I'd definitely move on to new examples even if you don't feel like you can play an example up to speed yet. You can always come back later! And when you practice the more difficult examples, it will "level up" your technique and the more simple examples will be even easier.
In the video, I say something like this: "play slow until you're comfortable, and then move on to the next example.."
But, you don't have to master each example up to speed before you move on. Stay inspired - cause that will make you want to practice!
I don't have a certain bpm goal that you should reach before moving on. I just suggest you to keep playing and have fun! :)
Thanks for watching the lesson Stevie, and have a wonderful day! Kind regards/E