To keep the tips sharp it is best to just wet stone them for 1 minute after each use. If they are really dull then you can use a wheel but have a bucket of water next to it to cool the tip every few seconds to keep it cool so the glue and plastic does not soften and the tip come out of the basket or ferrule. Use the same length poles for roller skiing as snow skiing.
from the SkiPost readers:
… those tips are silicon carbide, so the best thing to sharpen them with would be a diamond file or diamond wheel. Regular grinding wheels are also made of silicon carbide, which would be the same hardness as the tip, so using a standard wheel could be frustrating….