It's great that you are planning a trip to Ireland!
These 3 ferry companies are indeed the only ones departing from France (Cherbourg and Roscoff). You can find an overview of the routes on this page
Alternatively, you can depart from Belgium and the Netherlands, but you'll have to cross the UK by car and take another ferry to reach Ireland. There is another direct route from Santander (Spain) to Rosslare (Ireland)
Will you be coming from France ?