A rotor-blade discharge unit enabling electric charges to be discharged from a rotor blade of a wind turbine, the rotor blade discharge unit comprising at least one current transfer arrangement, the current transfer arrangement comprising: a roller device (15, 16), an electrically conductive slideway, and a spark gap, wherein the roller device (15, 16) is biased towards the conductive slideway and is movable relative to the conductive slideway, the roller device (15, 16) comprising: at least one contact wheel (30A, 30B), having a rolling surface and the contact wheel is arranged to roll on the conductive slideway and is biased towards the conductive slideway, wherein the rolling surface is arranged to deform against the conductive slideway under the bias acting on the roller device (15, 16), wherein the contact wheel (30A, 30B) and the conductive slideway form a first current path to discharge the electric charges, wherein the spark gap forms a second current path upon occurrence of a spark bridging the spark gap, wherein the second current path is connected in parallel to said first current path, and wherein the contact wheel (30A, 30B) is made, at least in a region at the rolling surface, of elastomeric electrically conductive or semi-conductive plastics, or of electrically conductive carbonaceous materials having a Shore D hardness of 18 or less. a roller device (15, 16), an electrically conductive slideway, and a spark gap, wherein the roller device (15, 16) is biased towards the conductive slideway and is movable relative to the conductive slideway, the roller device (15, 16) comprising: at least one contact wheel (30A, 30B), having a rolling surface and the contact wheel is arranged to roll on the conductive slideway and is biased towards the conductive slideway, wherein the rolling surface is arranged to deform against the conductive slideway under the bias acting on the roller device (15, 16), wherein the contact wheel (30A, 30B) and the conductive slideway form a first current path to discharge the electric charges, wherein the spark gap forms a second current path upon occurrence of a spark bridging the spark gap, wherein the second current path is connected in parallel to said first current path, and wherein the contact wheel (30A, 30B) is made, at least in a region at the rolling surface, of elastomeric electrically conductive or semi-conductive plastics, or of electrically conductive carbonaceous materials having a Shore D hardness of 18 or less. at least one contact wheel (30A, 30B), having a rolling surface and the contact wheel is arranged to roll on the conductive slideway and is biased towards the conductive slideway, wherein the rolling surface is arranged to deform against the conductive slideway under the bias acting on the roller device (15, 16), wherein the contact wheel (30A, 30B) and the conductive slideway form a first current path to discharge the electric charges, wherein the spark gap forms a second current path upon occurrence of a spark bridging the spark gap, wherein the second current path is connected in parallel to said first current path, and wherein the contact wheel (30A, 30B) is made, at least in a region at the rolling surface, of elastomeric electrically conductive or semi-conductive plastics, or of electrically conductive carbonaceous materials having a Shore D hardness of 18 or less.