check user role from python and client side script

To check user role from client side

@frappe.whitelist(allow_guest=True)
def validate_role(self, method):
        user="kolate.sambhaji@gmail.com"
        frappe.msgprint(_("In role validate function"))
        role_list = frappe.db.sql("""select name,owner,parent,idx,role from tabUserRole where parent=%s and role='Blogger'""",
                user)
        if len(role_list) > 0:
            frappe.msgprint("user is blogger")
        frappe.msgprint(role_list) #this will test user role blogger

This will print  -1 if user role Account Manager is not present
If user role Account Manager is present, then first msgprint will print value greater than one

To check user role from python
1) frappe.get_roles() will give you all roles of current  user

2) to check other user role
You can use following(python) code to check particular user roles.

@frappe.whitelist(allow_guest=True)
def validate_role(self, method):
        user="kolate.sambhaji@gmail.com"
        frappe.msgprint(_("In role validate function"))
        role_list = frappe.db.sql("""select name,owner,parent,idx,role from tabUserRole where parent=%s and role='Blogger'""",
                user)
        frappe.msgprint(role_list) #this will test user role blogger

Above script will check user role for 'kolate.sambhaji@gmail.com', you can pass any user id to check its roles.