The town expanded significantly after Napoleon I chose the site as the new préfecture of the Vendée on 25 May 1804, replacing Fontenay-le-Comte (then under its revolutionary name of Fontenay-le-Peuple).

At the time, most of La Roche had been eradicated in the Vendée Revolt (1793–96); the renamed Napoléonville was laid out and a fresh population of soldiers and civil servants was brought in.

The population data in the table and graph below refer to the commune of La Roche-sur-Yon proper, in its geography at the given years.

The Gare de La Roche-sur-Yon railway station offers connections to Nantes, Paris, Les Sables-d'Olonne, Bordeaux and several regional destinations.

[20] La Roche-sur-Yon's Vendéspace hosted one of the first round ties of the 2014 Davis Cup tennis tournament over the weekend of 31 January - 2 February 2014.

In June 2015 La Roche-sur-Yon's Vendéspace will host the qualification tournament for the World Championships in Savate Combat.