The wet look is the oil from the coffee bean. This usually indicates a dark roast about CS 10-11-12. When you roast about CS 8-9 or lighter (I normally roast to CS 9-11) the beans usually dont develop much oil. The oil can also come out when the beans have aged so check the date they were roasted.
The CS numbers relate to the colours on the Membership Card you can get throught Beanbay.