Be different and unique. Remember the other coffee shops near you are not only competitors, they also bring customer flow to the area!
We know that those loving their dark roast are not going to drink light roasted coffee if they are not forced to. And there are always people who want their coffee crispy and fruity as well as people who want their coffee chocolaty and nutty. Have at least two choices of coffee to get more customers. You can also change them on a regular basis to keep the selection interesting. Remember the non-coffee drinkers, too!