One table, many references

I'm a total newby to Ruby and jumped into an application that quickly went
over my head. My question relates to how I can setup the models in my app
so that I can reference the same database table using different names.
Here's how my database is setup:

table requests
  id
  title
  sponsor_id
  initiator_id
  implementor_id

table employees
  id
  fname
  lname

The sponsor_id, initiator_id, and implementor_id fields are all intended to
reference an row in the employees table. I'm confused as to how I make
rails understand that these foreign keys all reference the same table. Can
anyone help?