Here's a breakdown:
* "Roth" means "red"
* "Haar" means "hair"
* "iger" is a suffix that makes it an adjective meaning "having red hair"
You can also use the more informal "Rothaarige" for a woman.
Here are some other options, depending on the context:
* "Rotschopf" (literally "red top") - often used as a nickname for someone with red hair
* "Feuerkopf" (literally "fire head") - a more poetic and less common term
* "Kupferroter" (literally "copper-red") - describes someone with coppery red hair
Remember that "Rothaariger" is the most common and generally accepted term.