I'm not a fan of adding rollers or skid bars / plates at RV's rear. These items often add 1" - 2" depth and will make the dragging problem worse. Best is to lift the trailer a little higher.
As a suggestion, take your RV to a few welding shops in your area. (Google search is great for finding welding shops in one's area). They will view / understand your RV's current suspension parts and recommend different ways (or best way) to raise your trailer a few more inches higher. This could be simply drilling new holes in existing steel hangers. Or, re-position the axles under the leaf packs and/or doing both. re: Raise 6", then lower down 3" with new holes in hanger brackets. Or, they might even suggest a lift kit / spacer tubes - if this is better.