Thank you, it's a post full of caffeine! The acidity is dictated by the variety of coffee, roasting can affect a range of flavours in the bean - roast too quickly and it will be undeveloped or for too long and the coffee will be baked. The darker the roast when you roast for longer then strength increases and also the bitterness, you can also start to get a burnt taste.
I prefer a light roast that suits brewing by filter, you can enjoy a range of flavours that way.