A roller cone drill bit for drilling earth formations includes a bit body having at least one roller cone rotably attached to the bit body and a plurality of cutting elements disposed on the at least one roller cone in a plurality of rows arranged circumferentially around the at least one roller cone, wherein at least one cutting element in the gage row, the heel row, or a surface of the at least one roller cone bounded by the gage and heel rows comprises thermally stable polycrystalline diamond or a thermally stable polycrystalline diamond composite. The at least one cutting element may be a TSD insert or a TSD composite insert and may be formed by brazing, sintering, or bonding by other technologies known in the art a thermally stable polycrystalline diamond table to a substrate. The interface between the diamond table and the substrate may be non-planar. A roller cone drill bit includes a bit body, at least one roller cone rotably attached to the bit body, and a plurality of cutting elements disposed on the at least one roller cone, where at least one of the plurality of cutting elements comprises thermally stable polycrystalline diamond or a thermally stable polycrystalline diamond composite and a cutting surface, wherein at least a portion of the cutting surface is contoured.