When making sushi/nori rolls how do I wash the bamboo roller?

I have tried making sushi a couple of times and not sure about how to wash the bamboo roller. Mine keep going mouldy. Is there some trick to stopping this happening, or are they one use only?
Update: Sorry if I seem really naive, but what is a saran wrap?
I haven't had much experience making foreign foods but would love to learn, but a lot of the techniques are very particular. Thanks for your advice
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