Raw support is camera specific. Aperture does not support all cameras. See the list of currently supported cameras here: Apple - Aperture - Technical Specifications - RAW Support
If your camera is relatively new, it might be supported in a later Digital Camera RAW Compatibility Update
Until your camera will be supported, consider to shoot RAW & JPEG, and import both, with the JPEG selected as original. You can switch to the RAW original later. Or import only the JPEGs, like before, and add later the RAW images as well.
Another option would be to use the software that came with your camera to develope the RAW and save the images in another lossless format, e.g. TIFF. Then import the TIFFs to Aperture.
Unfortunately Apple's RAW Support doesn't support any Samsung cameras. You can use the DNG converter from Adobe to convert the RAWs seperately. Afterwards you can import the DNGs to Aperture and merge them with the JPGs.
You can also give Apple feedback to support your Samsung camera with future updates. But Samsung isn't Apple's best friend.