That will be a manual effort. But my requirement is, when the user logs in, he should get one more role with snc_internal.

Okay, so what role do you want to assign? And is it for all users who log in? If yes, then create a Flow and add a condition to check if it’s their first login. Assign the role by adding the user to a group, and from there the user will get the role."

https://www.servicenow.com/community/developer-forum/how-do-i-add-a-user-to-a-role-in-flow-designer/...

we can go with the business rules as well right?

Thank you the solution.
can you please tell from where did you get to know that snc_internal should be stand alone role. Is there any business rule ? I tried to find that code/flow but no luck.