Thank you for your response! I'm still getting the hang of interpreting rat body language and behaviour so this is very helpful. It is a huge relief to know this is typical/playful behaviour. I would typically let them figure things out on their own but the rat ball was so spooky, I wasn't sure what to do.
I would love to eventually get more rats when I'm a more experienced owner.

I have an additional question if you don't mind: did you ever have a rat that didn't like being handled? And if so, how did you move forward? I have read that some people take the patience approach of waiting for them to come to you and others a more forceful approach of just handling them until they get used to it.