@schwabdinesh ideally you should be cloning the role as per each user's needs. Do you have a requirement where dashboards/alerts etc are strictly tied to users? i.e. dashboard1user1 tied with user user1 which no one else has access to. dashboard2_user2 tied with user2 which no one else has access to? How about administrators/power users or security team etc. should they not have access to these dashboards?
Splunk deals with access / permission on role level, not user level.
So for your question, the answer is, no, you cant do it.
the only way to achieve it, is to create a separate role for unique user for unique dashboard.
@niketnilay elaborated well on his comment above.