In Odoo v15, the REST API is implemented using the odoo.addons.web.controllers.main module. This module provides a set of routes that you can use to perform CRUD operations on various Odoo models.

To get a list of all the routes available for the REST API in Odoo v15, you can go to the Odoo documentation site and navigate to the "Web Controllers" section of the API documentation. Here is the direct link to that section

Go to the Odoo website: https://www.odoo.com/documentation/15.0/search.html?q=REST+API&area=default&check_keywords=yes#
 
In the API Reference page, you can find the available endpoints for the Odoo REST API, including those related to employees and timesheets.

To give you a quick idea of the endpoints available for employees and timesheets, here are some examples:

To retrieve a list of all employees: GET /api/v1/employees

To create a new employee: POST /api/v1/employees

To update an existing employee: PUT /api/v1/employees/{id}

To delete an employee: DELETE /api/v1/employees/{id}

To retrieve a list of all timesheets: GET /api/v1/timesheets

To create a new timesheet: POST /api/v1/timesheets

To update an existing timesheet: PUT /api/v1/timesheets/{id}

To delete a timesheet: DELETE /api/v1/timesheets/{id}

Please note that these are just examples and that the actual endpoints may vary depending on your Odoo configuration and the modules you have installed. Make sure to refer to the documentation for the full list of available endpoints and their parameters.