Good question. Yes, a lot of them do have certain roles.
For example, while you read this, cells called rods and cones in the retina of your eye collect information about what you are reading and pass it on to the optic nerve which runs from the back of your eye into your brain. The “job” of the neurons of the optic nerve is to pass this info further back into the brain to a region called the thalamus.
Some of the neurons in the thalamus start to process or make sense of this information and it is then relayed on again to your visual cortex. The visual cortex is at the top, back of your brain, a long way from your eyes! Thanks to all these other neurons, it gets the information from the rods and cones in your eyes and finishes off processing all the information so that you “see” what you are reading.
Without all these specific neurons and cells, you would not be able to read this now! Clever isnt it?
There are many examples of this in the brain – I hope this on e helps to answer your question!
I guess the reason why they have specific functions in the brain is so that we can do more complicated things. It also means the brain can be a bit smaller than if all the cells had to be able to do anything, we’d probably need more of them, or they’d have to be bigger.