Get all the security roles assigned to a user of a particular user selected in the lookup.

I have a user lookup field on a Form for example ;

Administrator : lookup

Marketing Manager : lookup

As soon as we select the user from the lookup and save the form then a JS code should fire which will get the value of the user and retrieve all the roles assigned to that user and compare to check whether he/she is a system Administrator(smiliar for marketing manager). Similarly I have lookups for other roles.

It should give an alert if the roles doesn't match.