I figured it out, but instead of deleting my post I figured I would post the solution.
All I needed to do was change .user.username to .displayName
let nameList= message.guild.roles.resolve('Role-ID').members.map(m=>m.user.username).join('
');
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…