In general, darker roasts tend to be less acidic than lighter roasts. This is because the roasting process itself helps to break down some of the acids present in the coffee beans. However, there can still be significant variation in acidity levels between different types of coffee, even within the same roast category. For example, coffees from Ethiopia tend to be naturally less acidic than coffees from other origins. So, if you're looking for a coffee that is low in acidity, you may want to try a dark roast Ethiopian coffee.