JAVASCRIPT

get discord.js role

let role = message.guild.roles.cache.find(r => r.id === "Role ID");

// The member you want to add the role to
let member = message.mentions.members.first();

// Add role to the member
member.roles.add(role);

// Or add it to yourself
message.author.roles.add(role);

discord.js find role by name

let role = message.guild.roles.cache.find(role => role.name === "Rolename");