New entity required in an existing ManyToMany

I have two entities: Project.java and Employee.java that are ManyToMany mapped with each other (internally using the Hibernate generated table emp_project_mapping).

Now, I have a new one: Role.java that is to be mapped with above mentioned entities such that an employee in a project can have only one role. Also, this mapping should use that same mapping_table emp_project_mapping.

I have no idea how to achieve this scenario. Please help me out.

Employee.java

package com.ayush.springbootApp.bootCrudApi.model;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinTable;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToMany;
import javax.persistence.OneToOne;
import javax.persistence.Table;

import com.ayush.springbootApp.bootCrudApi.model.Project;
import com.ayush.springbootApp.bootCrudApi.model.Workstation;

@Entity
@Table (name="employee_table")
//model class for Employee
public class Employee {
    
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column
    private Integer id;
    @Column
    private String name;
    @Column
    private String gender;
    @Column
    private String department;
    @Column
    private String designation;
    @Column
    private Date dob;
    @Column(name="empcode",nullable=false,unique=true)
    private String empCode;
    
    @OneToOne(mappedBy="emp")
    private Workstation workStation;
    
    @ManyToMany
    @JoinTable(name="emp_project_mapping",joinColumns=@JoinColumn(name="emp_id"),inverseJoinColumns=@JoinColumn(name="project_id"))
    private Set<Project> prj=new HashSet<Project>();
    
    
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public String getDepartment() {
        return department;
    }
    public void setDepartment(String department) {
        this.department = department;
    }
    public String getDesignation() {
        return designation;
    }
    public void setDesignation(String designation) {
        this.designation = designation;
    }
    public Date getDob() {
        return dob;
    }
    public void setDob(Date dob) {
        this.dob = dob;
    }
    
    public String getEmpCode() {
        return empCode;
    }
    public void setEmpCode(String empCode) {
        this.empCode = empCode;
    }
    public Set<Project> getProject()
    {
        return this.prj;
    }
    public void setProject(Set<Project> prj)
    {
        this.prj=prj;
    }
    
    @Override
    public String toString() {
        return "Employee [id=" + id + ", code="+ empCode + ", name=" + name + ", gender=" + gender + ", department=" + department
                + ", designation=" + designation + ", dob=" + dob + "]";
    } 
}

Project.java

package com.ayush.springbootApp.bootCrudApi.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
import com.ayush.springbootApp.bootCrudApi.model.Employee;

@Entity
@Table(name="projects_table")
public class Project{
    
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column
    private Integer id;
    @Column(nullable=false)
    private String oea_number;
    @Column(nullable=false)
    private String project_name;
    @Column
    private String client_name;
    @Column
    private String origin_country;
    @Column(nullable=false)
    private Integer po_amount;
    @Column
    private int project_active;
    
    @ManyToMany(mappedBy="prj")
    private Set<Employee> emp=new HashSet<Employee>();
    
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getOea_number() {
        return oea_number;
    }
    public void setOea_number(String oea_number) {
        this.oea_number = oea_number;
    }
    public String getProject_name() {
        return project_name;
    }
    public void setProject_name(String project_name) {
        this.project_name = project_name;
    }
    public String getClient_name() {
        return client_name;
    }
    public void setClient_name(String client_name) {
        this.client_name = client_name;
    }
    public String getOrigin_country() {
        return origin_country;
    }
    public void setOrigin_country(String origin_country) {
        this.origin_country = origin_country;
    }
    public Integer getPo_amount() {
        return po_amount;
    }
    public void setPo_amount(Integer po_amount) {
        this.po_amount = po_amount;
    }
    public int getProject_active()
    {
        return this.project_active;
    }
    public void setProject_active(int project_active)
    {
        this.project_active=project_active;
    }
    public Set<Employee> getEmployee()
    {
        return this.emp;
    }
    public void setEmployee(Set<Employee> emp)
    {
        this.emp=emp;
    }
    
    @Override
    public String toString() {
        return "Project [id=" + id + ", oea_number=" + oea_number + ", project_name=" + project_name + ", client_name="
                + client_name + ", origin_country=" + origin_country + ", po_amount=" + po_amount + "]";
    }
    
    
}

Role.java

package com.ayush.springbootApp.bootCrudApi.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name="Employee_roles")
public class Role
{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;
    
    @Column(name="description",nullable=false)
    private String desc;
    
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getDesc() {
        return desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }
    
    
}

emp_project_mapping table