In order to simulate a component Multisim needs a SPICE model of that component. Unfortunately it appears ROHM does not publicly distribute SPICE models for this part, and there are no real equivalent parts in the Multisim database.
If you do have a SPICE model, you can create a custom component using our Component Wizard. A tutorial can be found here: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YH5fCAG&l=en-US
Otherwise, you can look for alternative parts from ROHM or other manufacturers that do have a public model available, or if you know the internal workings of the IC, you can create your own SPICE model from the equivalent macro circuit. An basic example of the latter can be found here: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA03q000000YHimCAG&l=en-US
