bot.on("message", async message => {
    if(message.content.startsWith("!rolelist")){
    let roleName = message.content.split(" ").slice(1).join(" ");

    //Filtering the guild members only keeping those with the role
    //Then mapping the filtered array to their usernames
    let membersWithRole = message.guild.members.filter(member => {
        message.guild.roles.find(r => r.name === 'yourrolename');
    }).map(member => {
        return member.user.username;
    })

    let embed = new Discord.RichEmbed({
        "title": `Users with the ${roleName} role`,
        "description": membersWithRole.join("\n"),
        "color": 0xFFFF
    });

    return message.channel.send({embed});
}