Roles allow you to create special privileges and profiles that specify what an agent can see and do within your Freshdesk support portal. These roles help you categorize your team into different sections, and assign them different capabilities so that they can do what they need to on their helpdesks without getting in each other's way. They're especially useful for larger teams, where there are different groups of employees trying to handle different areas. 

Default Roles:

By default, Freshdesk lets you choose between 4 roles for your team members:

  • Agents: Can view, respond to and assign tickets, as well as modify ticket properties.
  • Supervisors: Can view and respond to tickets, generate reports and can also enable automatic ticket assignment of the member groups under the Admin tab.
  • Admins: Can access everything and edit configurations under the Admin tab, but cannot view or modify billing information. 
  • Account Admins: Have complete access to everything, including billing and account management.

Custom Roles:

Custom roles in Freshdesk lets you create profiles for agents that define the level of access each of them will have in your support portal; that is, you can dictate what you'd like each agent to see, do, and act on.

Article- https://support.freshdesk.com/support/solutions/articles/97077-how-to-create-a-new-custom-role-and-why- 

How to assign a role to an agent
  • Go to Admin > Roles.
  • The number of agents belonging to each role will be displayed; just click on a role to add more agents to it
Alternatively, you can assign roles when adding/editing an agent:
  • Login to your helpdesk portal as an Admin.
  • Go to Admin > Agent to add a new agent (or hover over an existing agent in your list and click Edit.)
  • Scroll down to the Roles and Scope section, and click Associate roles.
  • Check all the roles that you want to assign to this agent.

Each time you add a new agent to your helpdesk, you'll have to specify their role. Once you apply a role to an agent, the agent will no longer be able to view or access options or updates outside their role. For example, if an agent has the role of Agent, they won't be able to see the Admin tab.
 
If you assign multiple roles to an agent, the highest privileges allowed across these roles will apply. For example, if you have one role that gives a user access to your Community Forums and another that allows them to Reply to Tickets, a user with both roles will be able to access your community forums and reply to tickets.