1. Rohan: Supervisory level
2. Sohan: Middle level
3. Mohan: Top level
As, Rohan said "he is going to I have purchased two new machines and it has become very difficult to motivate workers at shop floor to use these machines". This indicates that Rohan is responsible for worker level work that is supervising.
As, Sohan said "I am facing problems in finding the exact number and types of employees for my department". This indicates that Sohan is not directly dealing with workers, he is finding employees that is middle management work.
As, Mohan said I have to decide the long term plans of organisation and I am responsible for the overall welfare of the organisation this indicates that he have thoughts about future of the company which indicates top level management.