Start off with a clear statement like
“Is it okay if I roll need on cloth gear?” or
“I’m just here for [item]”
Or make your own group without clothies
If I joined a group with a warlock and priest, I assume we’re all rolling over the same loot. I rarely make that assumption with druids/shamen. But being upfront gives each player a chance to decided if they agree or not before getting an hour deep into a dungeon run.