Hi Sukhveer,
As mentioned by Saurabh, You can restrict the authorization based on Profit Center or Cost Center.
I guess your security team would have created the roles just add the object type PRCTR and give the Profit center for the particular department to that user role. You would need two roles for each department created from the standard role which is K_REP_ALL this is master role for all the reports in SAP PS.
Your security/basis person would be able to help you in creating these roles just get them assigned to their users IDs. You can test it out using a Test user and assigning these roles.
Hope it clears your doubts.
Cheers
Sammar