Anchor roller is bolted on, with spacer woodblock to keep it level. See interior photo for backing plate (1/4 inch aluminum) for the two bolts beside each other. See exterior photo from underneath, for shaped wood backing plate for forward bolt.
This might be the roller we used, but I'm not perfectly sure – the one in this link might be too short. https://www.defender.com/product3.jsp?name=windline-universal-stainless-steel-anchor-bow-roller&path=-1|2276108|2276122|2304756&id=31616