Thanks, that dll worked. I couldn't get Rocksmith (launched straight from Steam) to see any of the DLCs, not even Cherub Rock. I installed RS using Lutris and Cherub Rock showed up.. then I put the .dll in the wineprefixes windows/windows32 -directories, used winecfg to add d3dx9_42.dll into libraries, switched it to "native".. copied the downloaded CDLCs into the dlc -directory where the cherub rock was already.. and now everything works.
Anyone got even the official DLCs to work with RS launched straight from native Steam?