Anyone with the Heal spell can heal.
Many people will have spells such as Heal Area as well.
In older versions of RQ, people could make and use Healing Potions, they'll hopefully appear in the Gamesmasters Book.
You could have a dedicated Healer, but they are not that common.
In Glorantha there are several healer cults but most are non-combative and have limited spells. Outside Glorantha there may be other healer cults or schools, but many will be gentle souls, not suited to adventuring.
RuneQuest, more than any system I've seen, has self-healing spread throughout the game, so everyone is a healer.