What import settings have you tried? What configuration do you want the library to have (Both RAW + JPGs as separate masters or only one of them as master?).
If you want the RAW as master try importing as Both (RAW as master) to see if the preset is only applied to the RAW.
If you want both as masters, that is you're importing Both (Separate masters) then I don;t believe it will be possible to restrict the preset to just the RAWs on import. But instead of importing the images in two separate batches it might be easier to import both and to apply the preset after import using Metadata->Batch Change. It would be easy to filter just the RAW images to apply the preset to.