Report on Accounts without Opportunities in Professional edition

Create a Custom Roll-Up Summary Field on the Account Object

• Click Setup.
  Salesforce Classic: Customize | Accounts | Fields
  Salesforce Lightning: Object Manager | Account | Fields & Relationships
• Click New Custom Field, then set the Data Type as Roll-Up Summary.
• For 'Field Label,' enter Opportunity Count, then click Next.
• For 'Summarized Object,' select Opportunity.
• For 'Roll-Up type,' select Count, then click Next.
• Click Next, then click Save.

Create a Report Using the Account Object

1. Click Reports | New Report.
2. Select the Accounts Report type, then click Create.
3. Select the All Accounts and Date fields per your requirements.
4. Drag the Opportunity Count field into the filter and set the Criteria as Opportunity Count equals 0.

This report displays all Accounts without Opportunities in Salesforce Professional Edition.