Smarty is one of Rollan's orphan friends.
Smarty is most likely dimwitted or a smart aleck, as it is stated by Rollan that his name is not a compliment, but a joke. In Wild Born, he and Rollan were trying to get some willow extract for Digger. Unfortunately for Rollan, Smarty rushed into the apothecary and stole the extract before Rollan got the chance to sway the shopkeeper. As a result, Rollan was thrown in jail for a short period of time.
Smarty probably gave Digger the willow extract, but it was never confirmed.