Roi Hayashi is a Japanese former child actor and voice actor born in Tokyo, Japan, on March 8, 2001. He began his career in the entertainment industry at a young age, making his acting debut in 2007 with a role in the TBS drama series Daisuki! Itsutsugo Go3!!. His early work consisted primarily of television dramas and films, with his first voice acting credit coming in 2010.

In the realm of voice acting, Hayashi's most recognized role is Shigeru in the 2011 tokusatsu superhero film OOO, Den-O, All Riders: Let's Go Kamen Riders. This film, part of the long-running Kamen Rider franchise, is a crossover event featuring characters from the Kamen Rider OOO and Kamen Rider Den-O series. His performance as Shigeru represents a notable credit within a major Japanese action and science fiction property.

Beyond this, Hayashi provided voice work for the animated science fiction film Welcome to the Space Show, released in 2010, where he voiced the character Hiroto Nishimura. The majority of his on-screen appearances are live-action roles. His other acting credits include appearances in the television drama Steel Woman (Hagane no Onna) and its sequel, as well as roles in the live-action film adaptations of the Ninja Nonsense (Nintama Rantaro) series, where he played the character Kirimaru Settsu in 2011 and again in 2013. He also appeared in the 2012 film Strawberry Night.

Information regarding recurring collaborations with specific directors, producers, or other voice actors, as well as notable achievements such as awards or major recognitions solely for his voice acting, is not available.