It might be possible, but it might take a lot of work. As a first attempt, you need to go into the rosetta database, find the RNA parameter files and patches, and port them over into the fullatom residue type set. You might want to replace the DNA files with the RNA files if you have no DNA in your system. Once you’ve done that, you should be able to read RNA structures into the ligand docking application – I’m sure there will be pitfalls after that but I’m not sure where they’ll be…