Like all reptiles, ball pythons need a temperature gradient throughout their enclosure. A 'hot side' and a 'cool side'. This gives them the ability to thermoregulate themselves.
Like Slim said, 88-92 is pretty standard for the 'hot side'. And the 'cool side' should be around 80. Ball Pythons need that kind of heat as they do come from Africa after all. Any temperature under 75 is less than ideal and potentially dangerous. It can lead to regurgitation and respiratory infection. A basking temperature helps balls digest meals as well.
So since the temperature is currently 70, is that the ambient temperature? Are you using heat lamps, an under tank heat mat, or nothing? If you're using a heat source, what is the temperature of that? How are you reading temperatures.
Sorry for all the questions, but it really helps to determine the root of the regurge problem.
Night roaming is normal, so that's good to hear. If he was wandering during the day, that might be a little concerning.