Hi Sumeet,
I agree with Chandra that the admin team generally takes care of assigning the user/roles, but it all depends on the team structure you follow. In our team, I am the developer and I am responsible for assigning the user roles and taking care of the security as well. It is easier for one person to handle the assignment if he/she has created the user/roles. Save a lot of time and energy in communicating and re-communicating.