We can look into the lore for a second when it comes to spellcasters. 

LOTR is known for being a low fantasy setting. Any magic that is used, if at all, is usually subtle and not overly showy. Most magic users are High ranking Elves or Maiar like the Wizards. However, we do know that mortals can know sorcerous arts somewhat, because in the Hobbit, no one batted an eye or dispelled the notion that the "Necromancer" could be anything more than a man (and I am talking book lore, here). Gandalf also saying he was no "conjurer of cheap tricks" meant that there were conjurers, they were just at a lower tier than Gandalf and were probably only able to control enough magic to make simple illusions or fanciful lights. That and, of course, the Dwarves and Elves making magic gateways and weapons. 

If there was to be a spellcaster, they'd be pretty low class and probably a hermit or a delver of ancient lore. Most likely an Elf, or a very strange human.