Since "R20" is most commonly associated with the (popular in virtual tabletop roleplaying games like Roll20), I have interpreted your request as being about building a character’s personality for tabletop roleplaying games (TTRPGs) like Dungeons & Dragons or Pathfinder.
A personality is often defined by how they communicate. On the R20 interface, you can use the or /em commands in the chat to practice, but the real work happens in your head. personality builder r20