There is no train connection to Roses. If you want to go by train, travel to Figueres and then take a bus or taxi.
Directions are the same as to Figueres#By_plane and then take a bus or taxi.
Bus line from Figueres runs almost every hour and the price is 3.15€. There is a direct bus from Barcelona airport and Girona airport too. (bus timetables)
Taxi from Figueres costs around 40€ (December 2012).