David is right about 'olacak'. You can translate it as "it will be, it will become"
For "olarak", I woud like to give some examples:
Sen bir anne olarak, cocugunla ilgilenmelisin: being a mom (or since you are the mother of the child), you should take care of your child. In other words, if you hadnt been the mother, then you wouldnt need to show interest to him.
Yiyecek olarak pek bir sey kalmadi: There is not much left as food. In other words, there are some other things left but they dont belong to the group of 'food'
Ogretmen olarak bunu bilmek sana duser: Since you are a teacher, you are supposed to know it.
We define the property of an object or a person. We underline that property.